Previous in Forum: What Are Your Favorite Marketing 'Oops!' and Why?   Next in Forum: Looking for Paper Honeycomb Cores
Close
Close
Close
70 comments
Rating: Comments: Nested
Member

Join Date: Jan 2008
Posts: 9

Quiz/Brainteaser

11/07/2012 5:04 PM

To whom ever may know,

A while back I used to come on this website and i used to see a "weekly brain teaser"

or maybe it was daily. I don't remember does anyone know how to get to it?

Thank,

Omnib0mb3r

__________________
I have gone to find myself if I get back before I return keep me here
Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

"Almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, vote them!
Guru
Hobbies - DIY Welding - Don't Know What Made The Old Title Attractive... Popular Science - Weaponology - New Member United States - US - Statue of Liberty - 60 Year Member

Join Date: Apr 2009
Location: Yellowstone Valley, in Big Sky Country
Posts: 7425
Good Answers: 295
#1

Re: Quiz/Brainteaser

11/07/2012 5:10 PM

We now have a weekly What Is It? blog, which is pretty entertaining.

I think you are remembering the monthly Challenge Questions.

__________________
Semper Ubi Sub Ubi
Register to Reply
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#2

Re: Quiz/Brainteaser

11/07/2012 5:13 PM

Omnib0mb3r,

That's quite a clever brain teaser in itself. I give up. I have no clue.

Please PM the answer to me.

I will not reveal it to anyone.

Good Luck.

Register to Reply
Guru
Hobbies - DIY Welding - Don't Know What Made The Old Title Attractive... Popular Science - Weaponology - New Member United States - US - Statue of Liberty - 60 Year Member

Join Date: Apr 2009
Location: Yellowstone Valley, in Big Sky Country
Posts: 7425
Good Answers: 295
#3
In reply to #2

Re: Quiz/Brainteaser

11/07/2012 5:24 PM

I'll take a shot with 'OmniBomber'.

__________________
Semper Ubi Sub Ubi
Register to Reply
Power-User

Join Date: Nov 2011
Posts: 473
Good Answers: 13
#28
In reply to #2

Re: Quiz/Brainteaser

11/08/2012 10:29 PM

Omni bomber?

Hmmm, kinda scary!

Register to Reply
Guru

Join Date: Jun 2010
Location: New York
Posts: 972
Good Answers: 23
#4

Re: Quiz/Brainteaser

11/08/2012 8:51 AM

Here's a riddle for you:

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?

__________________
The first law of thermodynamics is you do NOT talk about thermodynamics.
Register to Reply Score 1 for Good Answer
Guru
Hobbies - DIY Welding - Don't Know What Made The Old Title Attractive... Popular Science - Weaponology - New Member United States - US - Statue of Liberty - 60 Year Member

Join Date: Apr 2009
Location: Yellowstone Valley, in Big Sky Country
Posts: 7425
Good Answers: 295
#5
In reply to #4

Re: Quiz/Brainteaser

11/08/2012 8:56 AM

You, Mizuti, are a hole (not a comment about you, that's my response to your riddle).

__________________
Semper Ubi Sub Ubi
Register to Reply Score 1 for Good Answer
Guru

Join Date: Jun 2010
Location: New York
Posts: 972
Good Answers: 23
#6
In reply to #5

Re: Quiz/Brainteaser

11/08/2012 9:05 AM

The equation shown below is not correct:
26-63=1
Can you make the equation correct by moving just one symbol?

__________________
The first law of thermodynamics is you do NOT talk about thermodynamics.
Register to Reply
Guru
Hobbies - DIY Welding - Don't Know What Made The Old Title Attractive... Popular Science - Weaponology - New Member United States - US - Statue of Liberty - 60 Year Member

Join Date: Apr 2009
Location: Yellowstone Valley, in Big Sky Country
Posts: 7425
Good Answers: 295
#7
In reply to #6

Re: Quiz/Brainteaser

11/08/2012 9:09 AM

Yes, I can:

26-63=1

__________________
Semper Ubi Sub Ubi
Register to Reply
Guru

Join Date: Jun 2010
Location: New York
Posts: 972
Good Answers: 23
#8
In reply to #7

Re: Quiz/Brainteaser

11/08/2012 9:14 AM

How many times a day does a clock's hands overlap?

EDIT: Don't use google!

__________________
The first law of thermodynamics is you do NOT talk about thermodynamics.
Register to Reply
Guru
Hobbies - DIY Welding - Don't Know What Made The Old Title Attractive... Popular Science - Weaponology - New Member United States - US - Statue of Liberty - 60 Year Member

Join Date: Apr 2009
Location: Yellowstone Valley, in Big Sky Country
Posts: 7425
Good Answers: 295
#9
In reply to #8

Re: Quiz/Brainteaser

11/08/2012 9:23 AM

The hands of an analog clock overlap every 65 minutes (+/-)... two trips around for the hour hand in one day... 22 times in 24 hours.

What's a Google? You're not the first guy to give me a pop quiz!

__________________
Semper Ubi Sub Ubi
Register to Reply
Guru

Join Date: Jun 2010
Location: New York
Posts: 972
Good Answers: 23
#10
In reply to #9

Re: Quiz/Brainteaser

11/08/2012 9:26 AM

If the probability of observing a car in 30 minutes on a highway is 0.95, what is the probability of observing a car in 10 minutes (assuming constant default probability)?

__________________
The first law of thermodynamics is you do NOT talk about thermodynamics.
Register to Reply
Guru
Hobbies - DIY Welding - Don't Know What Made The Old Title Attractive... Popular Science - Weaponology - New Member United States - US - Statue of Liberty - 60 Year Member

Join Date: Apr 2009
Location: Yellowstone Valley, in Big Sky Country
Posts: 7425
Good Answers: 295
#11
In reply to #10

Re: Quiz/Brainteaser

11/08/2012 9:38 AM

Exactly one car, or at least one car?

Somebody else join in... I do have to do a little bit of work today!

__________________
Semper Ubi Sub Ubi
Register to Reply
Guru

Join Date: Jun 2010
Location: New York
Posts: 972
Good Answers: 23
#12
In reply to #11

Re: Quiz/Brainteaser

11/08/2012 9:40 AM

0.95 is the probability for 1 or more cars, not the probability of seeing just one car.

What's the probability of seeing at least one car.

__________________
The first law of thermodynamics is you do NOT talk about thermodynamics.
Register to Reply
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#13
In reply to #12

Re: Quiz/Brainteaser

11/08/2012 9:54 AM

I can't see any cars from here.

Register to Reply Score 1 for Off Topic
Guru
Hobbies - DIY Welding - Don't Know What Made The Old Title Attractive... Popular Science - Weaponology - New Member United States - US - Statue of Liberty - 60 Year Member

Join Date: Apr 2009
Location: Yellowstone Valley, in Big Sky Country
Posts: 7425
Good Answers: 295
#14
In reply to #13

Re: Quiz/Brainteaser

11/08/2012 10:04 AM

__________________
Semper Ubi Sub Ubi
Register to Reply Off Topic (Score 5)
Guru
Popular Science - Weaponology - New Member United Kingdom - Member - New Member

Join Date: May 2007
Location: Harlow England
Posts: 16512
Good Answers: 670
#69
In reply to #13

Re: Quiz/Brainteaser

11/14/2012 11:34 AM

<splarf>
Del

__________________
health warning: These posts may contain traces of nut.
Register to Reply
Guru
Hobbies - DIY Welding - Don't Know What Made The Old Title Attractive... Popular Science - Weaponology - New Member United States - US - Statue of Liberty - 60 Year Member

Join Date: Apr 2009
Location: Yellowstone Valley, in Big Sky Country
Posts: 7425
Good Answers: 295
#15
In reply to #12

Re: Quiz/Brainteaser

11/08/2012 10:20 AM

Okay, got that customer fixed up... back top the important stuff

Well, the probability of seeing NO cars in 30 minutes is 0.05, so the probability of seeing no cars in 1/3 of that time is the cube root of 0.05.

Probability of seeing at least one car in 10 minutes is 1-(0.051/3), ≈ .63

__________________
Semper Ubi Sub Ubi
Register to Reply
Guru

Join Date: Jun 2010
Location: New York
Posts: 972
Good Answers: 23
#16
In reply to #15

Re: Quiz/Brainteaser

11/08/2012 10:46 AM

There is a number less than 3000 that when divided by 2 leaves a remainder of 1, when divided by 3 leaves a remainder of 2, when divided by 4 leaves a remainder of 3, When divided by 5 leaves a remainder of 4, when divided by 6 leaves a remainder of 5, and so on up to nine.

What is that number?

__________________
The first law of thermodynamics is you do NOT talk about thermodynamics.
Register to Reply
Guru
Hobbies - DIY Welding - Don't Know What Made The Old Title Attractive... Popular Science - Weaponology - New Member United States - US - Statue of Liberty - 60 Year Member

Join Date: Apr 2009
Location: Yellowstone Valley, in Big Sky Country
Posts: 7425
Good Answers: 295
#17
In reply to #16

Re: Quiz/Brainteaser

11/08/2012 11:17 AM

Let's find the least common multiple, and see if it's less than 3K.

N+1 must be a multiple of 2
N+1 must be a multiple of 4, but if a multiple of 2 and 4 it is a multiple of 8
N+1 must be a multiple of 5
N+1 must be a multiple of 6, but if multiple of 2 and 9 it's already a multiple of 6
N+1 must be a multiple of 7
N+1 must be a multiple of 9, thus multiple of 3

2×4×5×7×9=N+1= 2,520; Thus N = 2,519

Looks good from here. I see it works for 10 as well, remainder of 9.

__________________
Semper Ubi Sub Ubi
Register to Reply
Guru

Join Date: Jun 2010
Location: New York
Posts: 972
Good Answers: 23
#18
In reply to #17

Re: Quiz/Brainteaser

11/08/2012 12:01 PM

How much wood would a woodchuck chuck if a woodchuck could chuck wood?

__________________
The first law of thermodynamics is you do NOT talk about thermodynamics.
Register to Reply
Guru
Hobbies - DIY Welding - Don't Know What Made The Old Title Attractive... Popular Science - Weaponology - New Member United States - US - Statue of Liberty - 60 Year Member

Join Date: Apr 2009
Location: Yellowstone Valley, in Big Sky Country
Posts: 7425
Good Answers: 295
#19
In reply to #18

Re: Quiz/Brainteaser

11/08/2012 12:10 PM

How many times does the letter 'F' -either in
upper or lower case-appear in the following
sentence:

Finished files are the result of years of
of scientific study combined with the
experience of years.

This, a slight variation of an old favorite.

__________________
Semper Ubi Sub Ubi
Register to Reply
Guru

Join Date: Apr 2011
Posts: 8006
Good Answers: 286
#22
In reply to #19

Re: Quiz/Brainteaser

11/08/2012 1:31 PM

Only two 'F's is the answer.

The instructions are asking about the 'f's in the sentence that follows, but a colon does not complete a sentence, so the sentence in bold is still part of the same original sentence, so it can't be considered the 'following sentence'.

The last remaining sentence has only two 'f's.

__________________
Eternal vigilance is the price of knowledge. - George Santayana
Register to Reply
Guru
Popular Science - Weaponology - New Member Hobbies - Fishing - New Member

Join Date: May 2007
Location: Aloha or
Posts: 659
Good Answers: 19
#35
In reply to #19

Re: Quiz/Brainteaser

11/09/2012 4:04 PM

5

__________________
Closed biased minds are utterly impervious to any factual evidence which contradicts their beliefs
Register to Reply
Guru
Hobbies - DIY Welding - Don't Know What Made The Old Title Attractive... Popular Science - Weaponology - New Member United States - US - Statue of Liberty - 60 Year Member

Join Date: Apr 2009
Location: Yellowstone Valley, in Big Sky Country
Posts: 7425
Good Answers: 295
#38
In reply to #35

Re: Quiz/Brainteaser

11/09/2012 4:28 PM

Nope, not 5:

Finished files are the result of years of
of scientific study combined with the
experience of years.

Note the double appearance of the the word of, ending and beginning a line.
I had this one on an aptitude test... yikes, who looks for typos in an aptitude test? Not a typo, part of the test.

__________________
Semper Ubi Sub Ubi
Register to Reply
Anonymous Poster #1
#32
In reply to #18

Re: Quiz/Brainteaser

11/09/2012 2:36 PM

A woodchuck would chuck all the wood he could chuck,

if a woodchuck could chuck wood.

Register to Reply
Guru

Join Date: Jun 2010
Location: New York
Posts: 972
Good Answers: 23
#33
In reply to #32

Re: Quiz/Brainteaser

11/09/2012 2:42 PM

That's one answer; however, I like to believe it is actually 361.923 cubic centimeters a day, if only because it sounds more pretentious

Sauce

__________________
The first law of thermodynamics is you do NOT talk about thermodynamics.
Register to Reply
Anonymous Poster #1
#34
In reply to #33

Re: Quiz/Brainteaser

11/09/2012 3:13 PM

Was that an African or European woodchuck?

Register to Reply
Power-User
Engineering Fields - Control Engineering - Control Engineering Technical Fields - Education - Industrial Training Engineering Fields - Manufacturing Engineering - Manufacturing Training Engineering Fields - Electrical Engineering - Electrical engineering Training Engineering Fields - Instrumentation Engineering - Instrumentation Engineering United States - Member - New Member Engineering Fields - Energy Engineering - Become part of the larger group, change your world.

Join Date: Apr 2005
Location: Las Vegas, NV
Posts: 266
Good Answers: 1
#58
In reply to #18

Re: Quiz/Brainteaser

11/12/2012 12:05 PM

As much as he could, if he would.

__________________
AB PLC Training onsite, On-Line, training software and more. BIN95.com
Register to Reply
Power-User

Join Date: Feb 2009
Location: CT USA
Posts: 258
Good Answers: 14
#66
In reply to #18

Re: Quiz/Brainteaser

11/12/2012 4:30 PM

Just as much wood as a woodchuck could, if a woodchuck could chuck wood.

Register to Reply
Guru

Join Date: Apr 2011
Posts: 8006
Good Answers: 286
#21
In reply to #16

Re: Quiz/Brainteaser

11/08/2012 1:24 PM

1259

__________________
Eternal vigilance is the price of knowledge. - George Santayana
Register to Reply
Guru
Hobbies - DIY Welding - Don't Know What Made The Old Title Attractive... Popular Science - Weaponology - New Member United States - US - Statue of Liberty - 60 Year Member

Join Date: Apr 2009
Location: Yellowstone Valley, in Big Sky Country
Posts: 7425
Good Answers: 295
#23
In reply to #21

Re: Quiz/Brainteaser

11/08/2012 1:35 PM

Doesn't work for 8. Leaves a remainder of 3.

__________________
Semper Ubi Sub Ubi
Register to Reply
Guru

Join Date: Apr 2011
Posts: 8006
Good Answers: 286
#24
In reply to #23

Re: Quiz/Brainteaser

11/08/2012 1:42 PM

right you are.... yours is the only under 3000 then.

__________________
Eternal vigilance is the price of knowledge. - George Santayana
Register to Reply
Guru
Hobbies - DIY Welding - Don't Know What Made The Old Title Attractive... Popular Science - Weaponology - New Member United States - US - Statue of Liberty - 60 Year Member

Join Date: Apr 2009
Location: Yellowstone Valley, in Big Sky Country
Posts: 7425
Good Answers: 295
#25
In reply to #24

Re: Quiz/Brainteaser

11/08/2012 1:44 PM

I believe you are correct about #19. And I thought I was such a smarty-pants!

__________________
Semper Ubi Sub Ubi
Register to Reply
Participant

Join Date: Nov 2012
Posts: 1
#29
In reply to #4

Re: Quiz/Brainteaser

11/09/2012 7:33 AM

Light

Register to Reply
Guru

Join Date: Jun 2010
Location: New York
Posts: 972
Good Answers: 23
#30
In reply to #29

Re: Quiz/Brainteaser

11/09/2012 8:48 AM

Hmm, I suppose if you define "lighter" as "having more light" then yes, that'd be a correct answer as well!

Traditionally, the answer to the riddle is "a hole".

__________________
The first law of thermodynamics is you do NOT talk about thermodynamics.
Register to Reply
Guru

Join Date: Mar 2011
Location: Sebastopol, California
Posts: 1205
Good Answers: 54
#31
In reply to #4

Re: Quiz/Brainteaser

11/09/2012 9:28 AM

Space

__________________
Most people are mostly good most of the time.
Register to Reply
Guru

Join Date: Apr 2011
Posts: 8006
Good Answers: 286
#20

Re: Quiz/Brainteaser

11/08/2012 1:11 PM

You are in a row boat.

.

The row boat is floating in the pool that is 10ft long by 20ft wide by 5 feet deep. The boat is floating freely not touching any side nor the bottom.

.

The waterline on the boat at current level as well as a few inches above and below creates a rectangle 4 ft wide by 6 ft long. Your highly adept sense of balance enables you to stabilize and level the boat to maintain the waterline dimensions within a minute or so after any changes.

.

With you, in the floating row boat is a bowling ball 8 inches in diameter (with no finger holes) weighing 16 lbs.

.

The (liquid) water, row boat, bowling ball and you are all very close to the same temperature.

.

Because this brain teaser has taken so long to set up, making your time at pool unbearably long, you have become dehydrated (even though the pool is filled with pure deionized water, which you could have consumed) and less than perfectly rational. You suddenly feel outraged that there are no holes drilled in the bowling ball, and decide it should be tossed overboard.

.As you are sending the bowling ball overboard, the boat gets a bit tippy, and takes on exactly 16 pounds of water as you send the ball over. You and the row boat recover and the ball sinks to the bottom.

.

Part 1

When the water is again calm, and neglecting any evaporation or precipitation, is the water level in the pool higher or lower now than it was before you threw the bowling ball into the pool.

Part 2

How much does the water level change?

__________________
Eternal vigilance is the price of knowledge. - George Santayana
Register to Reply
Guru
Hobbies - DIY Welding - Don't Know What Made The Old Title Attractive... Popular Science - Weaponology - New Member United States - US - Statue of Liberty - 60 Year Member

Join Date: Apr 2009
Location: Yellowstone Valley, in Big Sky Country
Posts: 7425
Good Answers: 295
#26
In reply to #20

Re: Quiz/Brainteaser

11/08/2012 2:32 PM

Well, I guess I'll play if nobody else wants to.

Volume of 16 lb ball is 269 in3. Volume of 16 lb of water is 443 in3. So a 16 pound swap will reduce the volume of water in the pool by 174 in3. The boat displacement will not increase and does not come into play here, so the pool level will drop.

How much? 174 in3 of water over 200 ft2 is a depth of .006 in. So... not very much.

__________________
Semper Ubi Sub Ubi
Register to Reply
Guru

Join Date: Apr 2011
Posts: 8006
Good Answers: 286
#27
In reply to #26

Re: Quiz/Brainteaser

11/08/2012 9:10 PM

Flawless.

__________________
Eternal vigilance is the price of knowledge. - George Santayana
Register to Reply
Power-User

Join Date: Nov 2011
Posts: 473
Good Answers: 13
#40
In reply to #27

Re: Quiz/Brainteaser

11/09/2012 9:16 PM

Flawless?...yeeeeahhh...ooh....almost!. The volume of the 8" diameter bowling ball is not 269 in3!

I'm just being a dink but think about it carefully for a sec. Somethin' is missing! (that's a hint)

Register to Reply
Guru

Join Date: Apr 2011
Posts: 8006
Good Answers: 286
#43
In reply to #40

Re: Quiz/Brainteaser

11/10/2012 2:14 AM

A solid sphere with no holes drilled (as specified twice in the original problem) has a volume of

(4pi/3)*r^3

A radius of 4 gives a calculated volume of 268.08257310.... which technically should round down to 268, but some conventions always round up and since this teaser was related to concepts not rounding, I deemed 269 to be well with spec.

__________________
Eternal vigilance is the price of knowledge. - George Santayana
Register to Reply
Power-User

Join Date: Nov 2011
Posts: 473
Good Answers: 13
#44
In reply to #43

Re: Quiz/Brainteaser

11/10/2012 2:23 AM

Doh!!...I missed the no holes part. Twice!

I'll go sit in the corner now. :-(

Register to Reply
Guru

Join Date: Apr 2011
Posts: 8006
Good Answers: 286
#45
In reply to #44

Re: Quiz/Brainteaser

11/10/2012 3:22 AM

Actually, when I first read your comment it made me kind of panic.

I recalculated but made an error in my calculation, using the diameter instead of the radius for the volume of the bowling ball (which made me think my original error had been only squaring instead of cubing to get volume, so I thought your hint of something missing referred to cubing versus squaring).

At that point I calculated the volume of the ball to be too large to sink, and thought I had screwed up royally by providing an unsolvable problem (since I specified the ball would sink). I don't know why this type of thing gets to me so easily, but I was red faced, hating the idea that I hadn't checked calculations better.

It took me a while to figure out what I had done wrong, and that it was originally correct. Amazing how far I can run astray with just the slightest encouragement..

__________________
Eternal vigilance is the price of knowledge. - George Santayana
Register to Reply
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#46
In reply to #43

Re: Quiz/Brainteaser

11/10/2012 7:54 AM

I think the reasons that some may take you to task is simply your obvious rounding error, totally unnecessary, conceptual or not.

I was taught that up to 0.5, but not including 0.5, you rounded down. Everything above 0.5, including 0.5 was rounded up, unless otherwise stated in the rules, assuming that rounding is allowed at all.....

Therefore 268.08257310 (assuming this value is accurate, I did not check) should have been rounded down......or was there a statement somewhere that said it had to be rounded up.

If it had been for example 268.825731, then rounding up would have been correct.

Sorry, but your rounding up is not accurate enough for standard math....

PS. Its strange that you had a trailing "0", why was that? Had you already removed some values? (not that it would make any difference to rounding up/down before the decimal point....)

__________________
"What others say about you reveals more about them, than it does you." Anon.
Register to Reply
Guru

Join Date: Apr 2011
Posts: 8006
Good Answers: 286
#47
In reply to #46

Re: Quiz/Brainteaser

11/10/2012 8:57 AM

You and I share the same rounding convention.

Here is what is going on:

I created a variant of a brain teaser I appreciated some time ago.

It was barely light work for Doorman who gave a solid explanation for detailing how he arrived at the answer.

The teaser was not about rounding conventions nor calculator proficiency. It was about buoyancy. His calculation of volume for the bowling ball was 269 in^3 when the calculation before reducing to significant digits would be approximately 168.082573.....

It would have been petty for me to refuse to commend his solution, holding something back on the grounds of rounding errors. Who knows maybe he approximates pi at 3.142.

In fact insisting on 168 would have been incorrect. In the problem I believe I actually only specified the ball had a diameter of 8 inches. not 8.0 not 8.00 so 200 would have been the reported amount, if it were asked for.

But in fact, that was not the requested calculation....and since additional error is introduced if you perform multiple rounding-to-significance processes along the way instead of just one at the end, it wouldn't have been a reasonable criticism for me to make.

Ultimately the final answer is not changed when it is reported in significant digits.

.

You are correct the trailing zero was a result of stopping before the entire reported series was complete.

.

Even though we share the same convention for rounding to significant digits, I have to disagree with your dismissal of the 'always round up' convention as not being accurate enough for standard math (of course I don't know your definition of 'standard').

There are several examples for which rounding-up is not just acceptable, it is necessary. the two areas immediately come to mind. Number theory has several algorithms related to modular arithmetic that necessitate rounding up. Statistics is another field for which in certain areas rounding up is the rule.

.

I came back to edit this in because I thought of another one.... When calculating the minimum requirement for something, it is certainly accurate enough for standard math to round up to the next integer. Doing otherwise would be wrong. Example: minimum number of divisions required to use simpson's rule for an equation with error bound to <=0.0001....... n must be an integer and any rounding must be done upwards (it also has to be even if I remember right)

__________________
Eternal vigilance is the price of knowledge. - George Santayana
Register to Reply
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#50
In reply to #47

Re: Quiz/Brainteaser

11/10/2012 4:18 PM

I did not see anywhere here where specific rules for rounding up/down were promulgated/specified.

Other rules can apply when specified as you point out, but they weren't specified here....

So standard rules apply.....its really that simple.

__________________
"What others say about you reveals more about them, than it does you." Anon.
Register to Reply
Guru

Join Date: Apr 2011
Posts: 8006
Good Answers: 286
#51
In reply to #50

Re: Quiz/Brainteaser

11/10/2012 4:29 PM

In standard rounding convention with which you and I are familiar, if 269 is incorrect, what do you propose in its place...given it is not a requested answer and that this is an informal conversation?

.

.

(in the interest of lively debate, I'm setting aside a commonly adhered to rule stipulating 'the person who offers the challenge, picks the winner')

(on another note, don't hold your breathe waiting for someone to specify rounding-up when dealing with something like minimum necessary divisions for error bound calculations or minimum required people. It won't be specified on a per incidence basis as it is never specified in any other way.

__________________
Eternal vigilance is the price of knowledge. - George Santayana
Register to Reply
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#61
In reply to #51

Re: Quiz/Brainteaser

11/12/2012 12:40 PM

Here is a link showing the three most basic rules of rounding, usually the first two are most commonly used:-

Rounding

I believe this is what you were looking for and if I can assist further just ask.

__________________
"What others say about you reveals more about them, than it does you." Anon.
Register to Reply
Guru
Hobbies - DIY Welding - Don't Know What Made The Old Title Attractive... Popular Science - Weaponology - New Member United States - US - Statue of Liberty - 60 Year Member

Join Date: Apr 2009
Location: Yellowstone Valley, in Big Sky Country
Posts: 7425
Good Answers: 295
#52
In reply to #46

Re: Quiz/Brainteaser

11/12/2012 10:10 AM

Hi guys... I have some observations about the puzzle from tinac, and my subsequent offered solution.

The questions, after the narrative:
When the water is again calm, and neglecting any evaporation or precipitation, is the water level in the pool higher or lower now than it was before you threw the bowling ball into the pool.
Part 2
How much does the water level change?

The question ...is the water level in the pool higher or lower. was answered. Could have been a guess, had a 50/50 shot at this one.

The question How much does the water level change? was also answered, but my less that exact "Not very much" could use some expansion, demonstrating the problem was understood and solved rather than some wild arsed lucky guess.

I expected more grief over volume of 16 lb of water is 443 in3. That is correct (enough) for 4° C, not 32° C (human skin temp, more or less), which was alluded in the narrative.

__________________
Semper Ubi Sub Ubi
Register to Reply
Guru

Join Date: Apr 2011
Posts: 8006
Good Answers: 286
#68
In reply to #52

Re: Quiz/Brainteaser

11/12/2012 9:23 PM

OK

.

The answer you provided was correct and accurate to the appropriate number of significant digits. The explanation of concepts was correct in all that it described. The level of analysis was appropriate given the explanation and the accuracy of the data provided.

.

I deemed that worthy of recognition as the right answer. In retrospect, at the insistence of now three separate protest, I beginning to understand my folly. My mistake was using calculation of a specific example eliminate guessing, but not following through with sufficient rigor once it had been established that the answer was based on correct analysis.

.

The criticisms are fair: even though the concepts are correct, every error, no matter how small has a chance to induce much larger significant error once a convention for rounding to significant digits is employed.

For example, when answers are to be reported to one significant digit, an error causing about a 1% reduction in the calculated final value before rounding (like the error introduced in the problem in question be using a volume based on a lower temperature), will cause no variation in the reported answer roughly 94% of the time. But when it does result in error, the error is large; at least low by 10% and possibly by as much as 50%.

.

The funny thing is that because of rounding conventions, for small errors ( smaller than 0.5/10^(number significant digits)) the percent variation in the as-rounded final answer, does not depend on the size of the error.

For example, in the flawed brain teaser i proposed, although the size an error which results in a lower before rounding calculated value does affect the likelihood that it will result in a different final rounded answer, because the final answer should be reported with only one significant digit, any error less than -5% that changes the rounded final answer, will result in an answer that is at least 10% low, and possibly 50% low.

Depending on the problem and even the units used, it is entirely possible that a seemingly insignificant variation of 0.0000000000000000000001% could result in answer that differed by at least 10% and up to 100%.

For example for answers with one significant digit if a pre rounded calculation is 1.499999999999999999999 after accounting for a very small effect but 1.500000000000000000000 before, once rounded to significant digits, failure to account for the effect results in a reported value 100% higher than if the effect is account for.

...

...

Which brings me back to the point. The inclusion or exclusion of incredibly small effects can influence answers (rounded to significant figures) to a degree far in excess of the relative influence on the problem as a whole.

This suggests that no influence no matter how small can be unequivocally deemed too small to affect an outcome.

In that case, given the vast number of possible (even though exceedingly small) influences, no analysis could be considered reasonably complete, unless....and this is the strange part... units can be utilized that yield an answer that is further away from any rounding mid point than the estimated maximum possible net effect of the remaining (not calculated) influences.

Does anyone do this? How do you get a decent idea of the remaining influences without falling prey to the self deception that you are cognizant of all possible influences?

As an example, in a situation similar to the brainteaser I presented, if the before-rounding answer (as calculated with consideration of all influences normally deemed of significance) were sufficiently close to a point where rounding changes from down to up, 6.499999999999999999999999999999999999999 for example, doesn't this necessitate taking into consideration a number of new previously overlooked influences?

- When the ball is dropped into the water and sinks to the bottom, this is a conversion of gravitational potential energy ultimately mostly into heat. This should cause a decrease in the water density (and bowling ball density) resulting in a different answer.

- Because the center of mass of the system lower at the end of the problem than the beginning, all other things being equal, the earth should spin slightly faster, decreasing the pressure felt by the water below from the water above, the small pressure coefficient of density would result in a very small increase in volume.

- There are no details about the draft of the rowboat or the particulars as to whether the rowboat lacks a scalloped keel which is likely to rest upon and transfer weight to the sunken bowling ball, yet floated free before it was cast overboard. While we might consider this very unlikely, even with a very low probability, the significant difference in end result should warrant consideration, given the very small effects of the things considered above.

.

.

As a result. i am declaring all people who attempt to answer or discuss the brain teaser to be wrong, including myself. Furthermore, as a person cannot be wrong if they provide the right answer, since all people are wrong, by necessity all answers are wrong. Ergo sum the question is moot.

.

Just one further note:

'.....The question ...is the water level in the pool higher or lower. was answered. Could have been a guess, had a 50/50 shot at this one......'

Actually there are three final conditions and so three possible answers to the question: higher, lower, neither.

I worded the question this way in hopes readers would notice my failure to mention the third option, and think I was attempting to obscure the correct answer; as many people initially think the water level is unchanged.

By the way this is not an unfair question. Technically, 'Is the water level in the pool higher or lower' is properly answered with 'yes' or 'no'. If one were intending to elicit 'higher' or 'lower' as answers, one solution would be to ask 'would the water level be higher or would the water level be lower.'

.

Brain teasers are too much work.

__________________
Eternal vigilance is the price of knowledge. - George Santayana
Register to Reply
Guru
Popular Science - Cosmology - Let's keep knowledge expanding Engineering Fields - Retired Engineers / Mentors - Hobbies - HAM Radio - New Member

Join Date: Dec 2006
Location: North America, Earth
Posts: 4528
Good Answers: 106
#36

Re: Quiz/Brainteaser

11/09/2012 4:12 PM

If a plane crashes on exactly the Utah/Kansas border, then in which state do they bury the survivors?

__________________
“I would rather have questions that can't be answered than answers that can't be questioned.” - Richard Feynman
Register to Reply
Guru
Popular Science - Weaponology - New Member Hobbies - Fishing - New Member

Join Date: May 2007
Location: Aloha or
Posts: 659
Good Answers: 19
#37
In reply to #36

Re: Quiz/Brainteaser

11/09/2012 4:14 PM

Why would you bury survivors?

__________________
Closed biased minds are utterly impervious to any factual evidence which contradicts their beliefs
Register to Reply
Guru
Popular Science - Cosmology - Let's keep knowledge expanding Engineering Fields - Retired Engineers / Mentors - Hobbies - HAM Radio - New Member

Join Date: Dec 2006
Location: North America, Earth
Posts: 4528
Good Answers: 106
#41
In reply to #37

Re: Quiz/Brainteaser

11/09/2012 11:45 PM

Very good, but there is no Utah/Kansas border.

__________________
“I would rather have questions that can't be answered than answers that can't be questioned.” - Richard Feynman
Register to Reply
Power-User

Join Date: Nov 2011
Posts: 473
Good Answers: 13
#42
In reply to #41

Re: Quiz/Brainteaser

11/10/2012 1:18 AM

Nice twist to an oldy.

Register to Reply
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#39
In reply to #36

Re: Quiz/Brainteaser

11/09/2012 4:49 PM

They usually let them go home......

__________________
"What others say about you reveals more about them, than it does you." Anon.
Register to Reply
Power-User
Engineering Fields - Control Engineering - Control Engineering Technical Fields - Education - Industrial Training Engineering Fields - Manufacturing Engineering - Manufacturing Training Engineering Fields - Electrical Engineering - Electrical engineering Training Engineering Fields - Instrumentation Engineering - Instrumentation Engineering United States - Member - New Member Engineering Fields - Energy Engineering - Become part of the larger group, change your world.

Join Date: Apr 2005
Location: Las Vegas, NV
Posts: 266
Good Answers: 1
#48

Re: Quiz/Brainteaser

11/10/2012 12:33 PM

If you where placed in a room with no doors and no windows. (like you where beamed into an indestructible titanium cube), and all that is in the room is a table and mirror. How do you get out?

This is a riddle I give to get my students to start them thinking out of the box. (pun intended)

__________________
AB PLC Training onsite, On-Line, training software and more. BIN95.com
Register to Reply
Power-User

Join Date: Nov 2011
Posts: 473
Good Answers: 13
#49
In reply to #48

Re: Quiz/Brainteaser

11/10/2012 1:13 PM

Not really a riddle. It's a play on words. Look in the mirror and see what you saw. Take saw and cut table in half. Put two halves together to make a whole. Crawl out the hole.

I've always found this one silly because it has no basis in reality.

You also can't mention "indestructible titanium cube" because then you could't make a hole in it. Right?

Register to Reply Score 1 for Good Answer
Power-User
Engineering Fields - Control Engineering - Control Engineering Technical Fields - Education - Industrial Training Engineering Fields - Manufacturing Engineering - Manufacturing Training Engineering Fields - Electrical Engineering - Electrical engineering Training Engineering Fields - Instrumentation Engineering - Instrumentation Engineering United States - Member - New Member Engineering Fields - Energy Engineering - Become part of the larger group, change your world.

Join Date: Apr 2005
Location: Las Vegas, NV
Posts: 266
Good Answers: 1
#60
In reply to #49

Re: Quiz/Brainteaser

11/12/2012 12:31 PM

Good job TerraMan, where had you heard this before? Yes, it is a play on words.

A "riddle" is defined as "a misleading question" which a play on words is misleading.

Also of note: Reality is a matter of perception, until you learn otherwise what is real. It used to be the world was square, until we learned a new reality. The Higgs - famously dubbed "the God particle," was only a theory, until they recently proved it, now it is reality.

The only true reality is that none of us will really know if it is real... we can only believe until something else in the infinate universe comes along to prove otherwise. he he

__________________
AB PLC Training onsite, On-Line, training software and more. BIN95.com
Register to Reply
Power-User

Join Date: Nov 2011
Posts: 473
Good Answers: 13
#65
In reply to #60

Re: Quiz/Brainteaser

11/12/2012 3:00 PM

"...where had you heard this before?"...University professor. Long time ago. I did not figure out the answer the first time I heard it. Way too "out of the box" for me.

You're right about reality. Depending on my mood, I often choose to substitute it with my own version!

Register to Reply
Guru

Join Date: Jun 2010
Location: New York
Posts: 972
Good Answers: 23
#53

Re: Quiz/Brainteaser

11/12/2012 11:23 AM

Joseph was terrified of the dark and of the Nightmare Werewolf, whom he feared would catch him out of bed in the dark. When Joseph went to bed, he would flip off the light switch on the far wall, then dash across the room to bed, 13 feet away.

However, yesterday he flipped the switch, walked slowly to his bed, and climbed in without a worry. Without using anything other than his finger to flip the switch, how did he manage to do this so calmly?

__________________
The first law of thermodynamics is you do NOT talk about thermodynamics.
Register to Reply
Guru
Hobbies - DIY Welding - Don't Know What Made The Old Title Attractive... Popular Science - Weaponology - New Member United States - US - Statue of Liberty - 60 Year Member

Join Date: Apr 2009
Location: Yellowstone Valley, in Big Sky Country
Posts: 7425
Good Answers: 295
#54
In reply to #53

Re: Quiz/Brainteaser

11/12/2012 11:36 AM

He went to bed while the sun was still up.

Sort of a big bedroom for a kid, isn't it?

__________________
Semper Ubi Sub Ubi
Register to Reply
Guru

Join Date: Jun 2010
Location: New York
Posts: 972
Good Answers: 23
#55
In reply to #54

Re: Quiz/Brainteaser

11/12/2012 11:39 AM

Kids today are spoiled.

Many miles away, a hunter left his camp early in the morning and tracked a bear due south for 10 kilometers. At this point the bear turned due west and went another 10 kilometers before the hunter caught up with him and shot him dead. The hunter then dragged the carcass of the bear back to his camp, a journey of exactly 10 kilometers. Given these facts can you tell me what colour the bear was?

__________________
The first law of thermodynamics is you do NOT talk about thermodynamics.
Register to Reply
Guru
Hobbies - DIY Welding - Don't Know What Made The Old Title Attractive... Popular Science - Weaponology - New Member United States - US - Statue of Liberty - 60 Year Member

Join Date: Apr 2009
Location: Yellowstone Valley, in Big Sky Country
Posts: 7425
Good Answers: 295
#56
In reply to #55

Re: Quiz/Brainteaser

11/12/2012 11:48 AM

Oh, come on... That's not how to spell 'color'.

__________________
Semper Ubi Sub Ubi
Register to Reply
Guru

Join Date: Jun 2010
Location: New York
Posts: 972
Good Answers: 23
#57
In reply to #56

Re: Quiz/Brainteaser

11/12/2012 11:49 AM

The 'u' makes it look more eloquent.. and more British.

__________________
The first law of thermodynamics is you do NOT talk about thermodynamics.
Register to Reply Off Topic (Score 5)
Guru
Hobbies - DIY Welding - Don't Know What Made The Old Title Attractive... Popular Science - Weaponology - New Member United States - US - Statue of Liberty - 60 Year Member

Join Date: Apr 2009
Location: Yellowstone Valley, in Big Sky Country
Posts: 7425
Good Answers: 295
#59
In reply to #57

Re: Quiz/Brainteaser

11/12/2012 12:06 PM

Aha! You've given a hint, allowing a me deduction.

There are no bears in Great Britain, but there are many deciduous trees and deciduous trees have leaves. There is a British musician, a mandolin player named Leafcutter John, who plays for an experimental jazz band named Polar Bear and as everyone knows a Polar Bear is white.

I have no idea what this has to do with your puzzle, but an amazing deduction, eh?

__________________
Semper Ubi Sub Ubi
Register to Reply
Power-User

Join Date: Nov 2011
Posts: 473
Good Answers: 13
#67
In reply to #59

Re: Quiz/Brainteaser

11/12/2012 4:39 PM

Wow!...You're like this guy!

Register to Reply
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#63
In reply to #55

Re: Quiz/Brainteaser

11/12/2012 12:43 PM

White?

__________________
"What others say about you reveals more about them, than it does you." Anon.
Register to Reply
Guru

Join Date: Jun 2010
Location: New York
Posts: 972
Good Answers: 23
#64
In reply to #63

Re: Quiz/Brainteaser

11/12/2012 1:07 PM

Winner winner chicken dinner!

__________________
The first law of thermodynamics is you do NOT talk about thermodynamics.
Register to Reply Off Topic (Score 5)
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#62
In reply to #53

Re: Quiz/Brainteaser

11/12/2012 12:42 PM

He switched the light on?

__________________
"What others say about you reveals more about them, than it does you." Anon.
Register to Reply
Member

Join Date: Jan 2008
Posts: 9
#70

Re: Quiz/Brainteaser

12/01/2012 3:46 PM

The location is the north pole and yes the bear would be white .

__________________
I have gone to find myself if I get back before I return keep me here
Register to Reply
Register to Reply 70 comments

"Almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, vote them!
Copy to Clipboard

Users who posted comments:

Andy Germany (6); BIN95 (3); Calnet42 (1); Deefburger (1); Doorman (18); lyn (2); Mizuti (13); Omnib0mb3r (1); rcwash1 (1); silvCrow (2); StandardsGuy (2); TerraMan (7); truth is not a compromise (10); user-deleted-1105 (1)

Previous in Forum: What Are Your Favorite Marketing 'Oops!' and Why?   Next in Forum: Looking for Paper Honeycomb Cores

Advertisement