‘So when is Cheryl’s birthday?’ Singapore math question for kids stumps internet

Never mind the color of that dress: When is Cheryl’s birthday? The latest viral puzzler to stump the Internet started out as a question for students in Singapore and spread around the world after it was posted here, reports the Washington Post.

The question isn’t as simple as it seems. It was first posted by Kenneth Kong on his Facebook page, who is television host in Singapore. It’s intended for sophomores and juniors participating in the Singapore and Asian Schools Math Olympiads, an annual brainiac competition.

But it’s baffling the entire world. Here’s the question:

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?

Ugh, Cheryl. Why does she have to be so difficult for an answer that’s probably posted on her Facebook account. If you’re stumped like us, New York Times science reporter Kenneth Chang posted a clearer version that might help you here.

Still stumped? There’s actually an answer, and no it’s not “black and blue.” Chang admits that the logic puzzle is “particularly convoluted” and it helps to write it out in a table. His dissection is long is so we’ll leave you to it.

Agencies/Canadajournal

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