It was meant to be a question to test teenagers at an elite high school in Singapore.

Albert and Bernard just become friends with Cheryl, and they want to know when her birthday is.

Cheryl gives them a list of 10 possible dates:

May 15/16/19

June 17/18

July 14/16

August 14/15/17

Cheryl then tells Albert and Bernard separately the month and the day of her birthday respectively.

Here are the hints ;

- 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 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 ?

It took me one freaking afternoon to get the answer !!!

Try not to find the answers from Internet....