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When's Cheryl's birthday?

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When's Cheryl's birthday?

A test was set for 14-year-olds in Singapore:
Quote
Albert and Bernard just became friends with Cheryl, and they want to know when her birthday is. Cheryl gives them a list of 10 possible dates.
May 15, May 16,  May 19
June 17, June 18
July 14, July 16
August 14, August 15, August 17
Cheryl then tells Albert and Bernard separately the month and the day of her birthday respectively.
Albert: I don’t know when Cheryl’s birthday is, but I know that Bernard does not know too.
Bernard: At first I don’t know when Cheryl’s birthday is, but I know now.
Albert: Then I also know when Cheryl’s birthday is.
So when is Cheryl’s birthday?

Edit: Wrong title - now changed

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9 REPLIES
Community Veteran
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Re: When's Cheryl's birthday?

Very clever Smiley A bit of logical thinking needed. I haven't given my answer in case others want to try first Wink
198kHz
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Re: When's Cheryl's birthday?

Cheryl is one of those annoying people who fill their bath tub with two taps at differing flow rates, with stopwatch in hand.
She won't get any birthday presents.  Wink
Not young enough to know everything
hmarshy
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Re: When's Cheryl's birthday?

July 16th?  Undecided
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Re: When's Cheryl's birthday?

Yes the 16th it is. Have a gold star.
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Re: When's Cheryl's birthday?

Yes that was my answer Smiley
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Re: When's Cheryl's birthday?

I often don't get the ones that don't jump out at me.....this one didn't jump Cry
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Re: When's Cheryl's birthday?

..........crept up on you Strat Wink
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Re: When's Cheryl's birthday?

http://www.nytimes.com/2015/04/15/science/answer-to-the-singapore-math-problem-cheryl-birthday.html?...
Call me 'w23'
At any given moment in the universe many things happen. Coincidence is a matter of how close these events are in space, time and relationship.
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Re: When's Cheryl's birthday?

Quote from: Strat
I often don't get the ones that don't jump out at me.....this one didn't jump Cry

Same with me.
@w23 Thanks for that link as the solution I had wasn't that clear (to me):

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