Monday 20 April 2015

Birthday headscratcher!

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 15May 16May 19
June 17June 18
July 14July 16
August 14August 15August 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?