So when is Cheryl's birthday?

[bluewraith]

This is from a math test in Singapore. Better get your thinking cap on.

 

[indyjohn]

Are we supposed to state the answer here?

 

[hopper68]

She is 29. All women seem to celebrate their 29th birthday year after year.

 

[Who Dares Wins]

June 17

 

[jagee]

At first I thought July 14, then I thought June 17, now I'm not sure.

 

[indyjohn]

Eliminating all the matching days leaves you with May 19th & June 18th.

The answer is May 19th, but I can't explain how I know that.

 

[jsharmon7]

July 16...BOOM!

 

[fullauto 45]

Who really cares, as long as she brings me my beer.

 

[BogWalker]

I would say May 19th. Albert says he does not know, and neither does Bernard. For some reason I get the feeling this means that months only on the list twice don't count. Not sure why, but that immediately came to me. Bernard says he knows when her birthday is after consulting the list. Bernard also has only the day, not the month. The only days that dont repeat are the 19th and 18th, and the only month on their three times with one of those two days is May. If he had had any other day than there would have been multiple pairings of months with that day, and therefore he would not be able to know what day it was she meant.

Or maybe the thing with Albert is switched around from how I figured it and the answer is June 18th.

 

[jsharmon7]

It helps if you write it out and mark off days as you eliminate them. You also have to take both of them at their word that they really know the answer.

 

[j4jenk]

July 16th

 

[BogWalker]

Just found the answer and explanation on Facebook. Can we go back to talking about the blue/black white/gold dress again instead?

 

[jagee]

Just found the answer and explanation on Facebook. Can we go back to talking about the blue/black white/gold dress again instead?

It's white and gold.



Now, what's the answer???

 

[Woobie]

July 16.

Albert knows Bernard does not know because the day falls in July or August. May and June have days that are not repeated elsewhere. If the day were the 18th or 19th, Bernard would already know the answer.

Bernard now understands because he was deciding between a number that occurred in either May or June and July or August. This eliminates the 14th of both those months.

Albert now knows it is July 16th because Bernard knows. If it had been in August, Albert, who knows the month, but not the day, would still have been left with 2 variables to chose from.

 

[Woobie]

Just looked up the Wikipedia page. There are two answers. The first can be arrived at by taking the statements of Albert and Bernard at face value and using basic logic. I won't say here, but the correct answer can be found on my, jsharmon7's or j4jenk's posts. There is also second answer. You have to make a couple of assumptions that really aren't given, and then proceed with some wacky logic, but you can arrive at the second answer that way.

 

[rgrimm01]

If they are teenagers, it is more likely that she is a figment of their imagination and therefore has no birthday...

 

[Who Dares Wins]

If they are teenagers, it is more likely that she is a figment of their imagination and therefore has no birthday...

They have to have some female friends!

 

[Who Dares Wins]

Here is a video of the explanation:-

Cheryl's Birthday: Singapore's maths puzzle baffles world - BBC News

 

[Dirtebiker]

June 17
no, July 16

 

[printcraft]

Why so sneaky Cheryl?

Cheryl just clevered her ass right out of a birthday present.