Challenge Questions Blog

### Challenge Questions

So do you have a Challenge Question that could stump the community? Then submit the question with the "correct" answer and we'll post it. If it's really good, we may even roll it up to Specs & Techs. You'll be famous!

Answers to Challenge Questions appear by the last Tuesday of the month.

 Previous in Blog: CR4 Challenge Question: Big clock in a New Year (Jan. 2022) Next in Blog: Challenge Question: Global Adventurer (March 2022)

# Challenge Question: Buckets and Quarts (Jan. 2022)

Posted January 30, 2022 12:00 AM
Pathfinder Tags: challenge question

You have two very plain, ordinary metal buckets. One is labelled 5 qt, the other 3 qt. But neither is graduated.

You have a spigot that provides endless water.

How do you arrive at exactly 4 quarts of water in one bucket?

Interested in this topic? By joining CR4 you can "subscribe" to

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
5
Guru

Join Date: Aug 2005
Posts: 5499
#1

### Re: Challenge Question: Buckets and Quarts (Jan. 2022)

01/30/2022 3:52 AM

Fill the three; empty into the five.

Fill the three; fill the five from the three.

Empty the five; pour the one remaining in the three into the five.

Fill the three; empty into the five.

You now have four in the five.

=======================================

Fill the five; fill the three from the five.

Empty the three; pour the two remaining in the five into the three.

Fill the five; fill the three from the five.

You now have four in the five.

=======================================

The first answer is just 3x3 - 5

The second is 2x5 - 2x3

So the first uses 9 quarts, and the second uses 10. But in the first you throw away 5 quarts, and the second only 3 (you still have 3 "spare" in the three bucket), so which is better depends on other circumstances.

__________________
We are alone in the universe, or, we are not. Either way it's incredible... Adapted from R. Buckminster Fuller/Arthur C. Clarke
Anonymous Poster #1
#9

### Re: Challenge Question: Buckets and Quarts (Jan. 2022)

02/22/2022 8:34 AM

These are the two we know about! Well done.

Guru

Join Date: Mar 2007
Location: by the beach in Florida
Posts: 31859
#2

### Re: Challenge Question: Buckets and Quarts (Jan. 2022)

01/30/2022 4:09 AM

Fill the 5 quart bucket and then fill the 3qt bucket using water from the 5 qt bucket, this will leave you 2 qts in the 5 qt bucket....mark that bucket at the 2 qt level...empty the 3 qt bucket and dump the remaining 2 qts from the 5 qt bucket into the 3 qt bucket...refill the 5 qt bucket to the 2 qt level you have marked, and add the contents of the water from the 3 qt bucket....you now have 4 qts in the 5 qt bucket...

__________________
All living things seek to control their own destiny....this is the purpose of life
2
Guru

Join Date: Dec 2010
Location: North West England
Posts: 1170
#3

### Re: Challenge Question: Buckets and Quarts (Jan. 2022)

01/31/2022 5:47 AM

Fit a flow meter calibrated to national standards to the spigot and meter out 4 quarts. This may not be an answer you were looking for but if you're daft enough to ask this question of engineers, it is an answer that was predictable.

Guru

Join Date: Mar 2007
Location: by the beach in Florida
Posts: 31859
#5

### Re: Challenge Question: Buckets and Quarts (Jan. 2022)

01/31/2022 7:03 AM

You could just weigh it...8.35 lbs = 4 qts....anybody can make a simple balance scale...

__________________
All living things seek to control their own destiny....this is the purpose of life
Associate

Join Date: May 2016
Location: Ohio, USA
Posts: 52
#4

### Re: Challenge Question: Buckets and Quarts (Jan. 2022)

01/31/2022 6:44 AM

__________________
If you cant say anything nice , dont say anything at all.
Off Topic (Score 5)
Active Contributor

Join Date: Mar 2020
Posts: 12
#6

### Re: Challenge Question: Buckets and Quarts (Jan. 2022)

01/31/2022 11:30 AM

fill 3 qt bucket, dump into five qt bucket, measure distance to top and mark half way using wide china marker. now fill to just top of the china markers mark and that should be correct. Not bottom, because bucket gets wider as it goes up, unless it is a straight sides bucket.

two other ways are mentioned above.. by others..

one final way- fill five gallon bucket. pour water from five gallon bucket to three gallon bucket, being careful. now throw away the three gallons.Mark the five gallon bucket inside where the remaining water was. pour that water into three gallon bucket and fill five gallon bucket to the line you marked. now add the amount in the three gallon bucket to the five gallon bucket, and you have four gallons.. and only wasted three gallons.

2
Guru

Join Date: Mar 2011
Location: Sebastopol, California
Posts: 1091
#7

### Re: Challenge Question: Buckets and Quarts (Jan. 2022)

01/31/2022 12:37 PM

1: Put the 3 inside the 5 and fill the 5 holding the 3 down inside but not filling the 3 but instead fill the space between the 3 and the 5.

2: Pull out the 3 and dump the 5 into the 3.

3: Put the 3 back inside the 5 and fill in between the 5 and 3 as in step 1.

4: Remove the 3 and dump it into the 5.

The 5 now contains 4 and only 4 has been used.

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

Join Date: May 2006
Location: Placerville, CA (38° 45N, 120° 47'W)
Posts: 6046
#8

### Re: Challenge Question: Buckets and Quarts (Jan. 2022)

01/31/2022 7:23 PM

Most of the answers so far apparently assume buckets that hold exactly the specified amounts of water when brim full. The OP does NOT say that; it says they are LABELED 3 qt and 5 qt. It also says that neither is graduated. It does not say whether there is a mark at the specified volume.

Every plain metal bucket I've ever seen, and that's quite a few, holds the specified amount with quite a bit of room to spare. A bucket labelled "3 quarts" will likely hold around 3.5 quarts when brim full, and there is no mark to indicate the specified water level. That circular indentation around the bucket (seen in the OP illustration) is to stiffen it, not to mark any particular water level.

Thus I say that replies #3 and #5 are the only correct ones so far...

__________________
Teaching is a great experience, but there is no better teacher than experience.
Interested in this topic? By joining CR4 you can "subscribe" to