When is Cheryl's Birthday? (Math Question)

I was miserable in math in high school. I joined the Navy not caring where I would end up. I remember the recruiter offering the job of aviation electrician and I explained the math thing. The recruiter said "Don't worry, they will teach you". I thought yeah right. The programmed instruction applied what you were learning to what you were going to use it for. The algebra, calculus, vectoring ect. came as some sort of revelation. It was amazing. So the article mentioning the curveball (A form of practical application?) as opposed to rote, rings true for me. Thanks for the article!

Oh what a goose I am! I thought I was supposed to comment on the article. I worked on the puzzle and found that Cheryl is Rosemary's baby,but that's as far as I could go. Ohwa tagoo siam!

July 16th. Went and checked and I got it right.

So is there a day of the week reference or something I am not seeing in the question?

Explain the logic and reasoning in detail please of where dates are not shared.

My calendar has dates for all 14,15,16,17,18,19 of those days in every month.

What it doesn't have is days 29, 30 and 31 in some months.

I'm missing something obvious here and not seeing it.

tcmtech, Cheryl gave the list of possible dates. Not every date is a possible date for her birthday because she eliminated many of them.

Thanks! I guess my brain is wired to rationalize and figure out more important real life practical application things.

Now you get one of my very rare GA votes.

I don't see how May can be eliminated all together, only May 19th, there are still 2 other days in May it could be, so not unique.

I agree that 6/18 and 5/19 are eliminated right away, since if it were a unique day Bernard would know. If Albert knew it was June then he would now know the date, but since his fist statement was he does not, it can be ruled out. Now Bernard does know and that's because 17 is now a unique date, since we just ruled out 6/17, thus leaving 8/17.

Shawn

Exactly, very well said.

Sorry Rixter, but I don't agree. Please follow this logic.

If it is May, 15 or 16, then according to your logic, Albert knows the month (May) and Bernard knows the day (15 or 16).

Statement one holds: Albert says Bernard cannot know the answer, since itcould be May 15 or August 15 (if he was given 15) or May 16 or Jul 16 (if he was given 16). You cannot remove May or June as choices. You can remove May 19 and Jun 18th only.

That logic does not hold. Albert does not know the day, only the month. The only way he can say with authority that Bernard does not know the full date is if the month is not May or June.

Think about it this way: Bernard is told 19. He now knows the full date, because there is only one date with a 19 (May 19).
-OR-
Bernard is told 18. He now knows the full date, because there is only one date with an 18 (June 18).

If Albert had been told May or June, he could not say that he is certain Bernard does not know the full date, because Bernard may have been told 18 or 19. Thereby, the month must be one of the two months that shares all of its possible day numbers with other months.

I was ready to argue with you and I saw the line where it says that Albert was given the month and Bernard the date. Something seems wrong with the first Statement. Let me think about it for a second.

I stand corrected. This is a pretty good problem!

Interestingly, I read that as Cheryl tells Albert the Month, and Bernard the day of the week: you can still get to a unique answer.

GA's to both Rixter and Randall. I went by Randall's day-of-week interpretation, constructed a chart similar to Rixter's, and reached the same answer. Nice puzzle.

Before she even tells them about it, they both know her birthday's got a unique date .

What happens if one is born right at midnight? Coin flip?

I replied to this post in a way that was a bit racy, but not unreasonably so. My reply was deleted. However, a whole string of Vipeak spam still exists. The slippage in moderation priorities is unfortunate.

I think the answer is Jun 17th. Please follow the logic:

1. Statement one gets rid of the two dates May 19th and June 18th - either one of the guys would have been given 18 or 19 and some would know her birthday.

2. Statement two eliminates Albert being given 14, 15, 16 for the following reasons:

a. If given 14, then Bernard given Jul or Aug. Bernard still doesn't know - could be Jul 14 or 16, or Aug 14, 15 or 17.

b. If given 15, then Bernard given May or Aug. Bernard still doesn't know - could be May 15 or 16, or Aug 14, 15 or 17.

c. If given 16, then Bernard given May or Jul. Bernard still doesn't know - could be May 15 or 16, or Jul 14 or 16.

3. Statement two eliminates Albert being given May, Jun, Jul or Aug for the following reasons:

a. If given May, then Bernard given 15 or 16. Bernard still doesn't know - could be May 15 or Aug 15, or May 16 or Jul 16.

b. If given Jun, then Bernard given 17. Bernard still doesn't know - could be Jun 17 or Aug 17.

c. If given Jul, then Bernard given 14 or 16. Bernard still doesn't know - could be Jul 14 or Aug 14, or May 16 or Jul 16.

d. If given Aug, then Bernard given 14, 15 or 17. Bernard still doesn't know - could be Jul 14 or Aug 14, May 15 or Aug 15, or Jun 17 or Aug 17.

4. We've eliminated everything except Albert being given 17, which means that Bernard was given Jun. From Statement 1, Jun 18th was eliminated. Since Bernard is the only on who knows it's Jun, that means that he knows its Jun 17th - agrees with Statement 2.

5. From Statement 2, Albert now knows that it can't be Aug 17 - Bernard would not have known it from Statement 1 (given Aug, he couldn't have known whether it was the 14, 15 or 17). The only option is Jun 17th and he states he knows it too.

Look up the word "respectively" in the dictionary.