The maths problem that stumped the Internet

A maths problem set for Singapore’s high school students has gone viral, leaving Internet users across the world frustrated after attempts to solve it.

The question was set for the “difficult” level of a test organised by the Singapore and Asian School Math Olympiads (SASMO) on April 8. Kenneth Kong, the presenter of “Hello Singapore”, a local television show posted it on his Facebook page on Saturday. Since then it has been driving people crazy across Internet.

So can you solve it?

Here is the problem. Try to figure it out without peeking at the solution below.

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?

The problem caused the hashtag #cherylsbirthday to trend on Twitter, with some posting detailed solutions while others questioned their methodology. Some unable to solve the problem blamed “Cheryl” for being too coy with the two boys.

But what is the ideal solution? SASMO itself put this up on their Facebook page:

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Printable version | Oct 22, 2021 5:51:07 AM |

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