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Cheryl has a birthday, and she doesn't want to share it right away. (Otherwise, we have no challenge to solve.)
So she gives her friends Albert and Bernard a list of 10 possible birthday dates: May 15, May 16, May 19, June 17, June 18, July 14, July 16, August 14, August 15 or August 17.
Cheryl then tells Albert and Bernard separately the month and the day of her birthday respectively.
We then have a conversation which progresses as below -
Albert: I don't know when Cheryl's birthday is, but I know that Bernard doesn't know too.
Bernard: At first I don't [sic] know when Cheryl's birthday is, but I know now.
Albert: Then I also know when Cheryl's birthday is.
So, it is possible to deduce Cheryl's birthday?
I'm surprised this was not posted here before. Its become fairly popular recently.
Of course, try to solve it without searching on the internet! Not much fun otherwise. 
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July 16. 
You have just been Sharapova'd.
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I could tell the answer just by looking at the problem - "Cheryl's Birthday". 
I ain't got no signature.
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Yes.
Life's like a nose, you've got to get out of it whats in it!
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Yes || No || Maybe
How do we preserve the wisdom men will need,
when their violent passions are spent?
- The Lost Horizon
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Here's another question:
Cheryl is 21 years older than her son. 6 years from now, she will be 5 times as old as him.
Question: where is the son's father? 
modified 27-May-15 7:03am.
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Researching into time travel? Actually baby not born yet so probably just unaware.
One day I aspire to having a signature.
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In jail, I hope...
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
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Someone else told me the same answer once. He made a mistake in his calculation. I guess you did too.
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Nah - I just don't like the guy...
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
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I guess the answer you're looking for is "in her"  (She's 20y3m old and the "baby" -9m)
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June 17 - ignore this, got Albert and Bernard wrong way round 
One day I aspire to having a signature.
modified 27-May-15 8:12am.
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I never got around to getting into the big deal about this - but as now it hit CP, I took a look. Not particularly difficulty (why was there such a (media/internet) fuss if this was the problem?) and yet a pleasant exercise as I rarely have time for these these days.
Presuming I got it right with July 16th, that is . . .
| "The difference between genius and stupidity is that genius has its limits." - Albert Einstein | | "As far as we know, our computer has never had an undetected error." - Weisert | | "If you are searching for perfection in others, then you seek disappointment. If you are seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010 |
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The big fuss was because it was set in a SAT style test for children 5 years younger than intended and all the little dears went home and cried to their over-protective parents who had failed to teach them that it was OK to admit that there are some things you can't do when you're 10 that you will be able to do when you're 15 and responded by attacking the education authorities rather than deal with their own lack of parenting skills.
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Well - in this case I understand the fuss - but on a different level.
To put that type of question on the test clearly calls into question the designer of the test. A test should be difficult enough to allow adequate differentiation amongst those taking it - so a test where no one gets 100% is ideal. On the other hand - putting material into a test is an implicit indication that you should know how to answer it. The injection of an unnerving experience into the test (unless it was for some reason testing this unnerving phenomenon) is incompetent if not outright sadistic.
Actually - you bring back a memory of my own in such a matter (and I always did very well on standardized exams): a question on a state-wide exam asked for what cause a certain person was famous. It turns out they were a furniture designer. That question was absolutely without any merit (and possible added so certain person's offspring can pick up an extra 4-pts). It lay completely out of place not only based upon standard curriculum, but beyond the knowledge and interests of all but a select few. But, back to the subject:
Perhaps the outrage of the parents is not incorrect, but merely misplaced - their should really be an inquiry into what motivated inclusion a question of such a nature. My view of psychologists and sociologists is that they'd not have any qualms about screwing with large numbers of children just to see how it affects them.
| "The difference between genius and stupidity is that genius has its limits." - Albert Einstein | | "As far as we know, our computer has never had an undetected error." - Weisert | | "If you are searching for perfection in others, then you seek disappointment. If you are seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010 |
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Well, yeah, except it was simply a clerical error. The papers for the two age groups were prepared together and the question was inadvertently transposed. As usual c**k-up was always far more likely to be the explanation than conspiracy!
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42
New version: WinHeist Version 2.1.1 new web site.
I know the voices in my head are not real but damn they come up with some good ideas!
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Jokers are not allowed, not even this one.
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Now this is the Cheryl on the cake.
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Helping your kid with their Common core again?
If it's not broken, fix it until it is
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I still don't see how to eliminate August 15 or August 17.
At the point Albert says Bernard doesn't know, It eliminates May and June. Bernards revelation that he knows only eliminates any that are the 14th. But his statement can be true for any of the remaining three dates. Bernard, in fact, WOULD know at this point because there is only one month left for each of the remaining numbers that Cheryl could have told him (15, 16, or 17).
Albert's final statement is merely a "hope" that he knows. He is guessing that because one of his months only has one day left that that is the month, but it could in fact be one of the August days, still.
The way to fix this would be to also include July 15 and July 17 in the list of possible dates.
Any comments? Did I miss something?
Brent
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Albert was told the correct month. So if he was told August, he couldn't say that he knows. That he can say confidently at the end that he knows the date, can only mean he was told July (assuming of course neither of the two was lying).
The good thing about pessimism is, that you are always either right or pleasently surprised.
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But that is my question. How can he "say confidently" when there is still a chance it could be August?
The prior quotes can and are perfectly accurate, but Albert's final comment cannot be. Unless the narrator wants to add "And he was correct" to the end of that line.
Brent
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Quote: Six football officials have been arrested over corruption charges at governing body Fifa and face extradition to the US, officials say.
http://www.bbc.co.uk/news/world-europe-32895048[^]
Every day, thousands of innocent plants are killed by vegetarians.
Help end the violence EAT BACON
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Nothing will happen, they'll just keep passing the ball.
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