Cheryl's Birthday: Singapore's maths puzzle baffles world

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Photo of the "Cheryl's Birthday" logic questionImage source, Kenneth Kong
Image caption,
The logic question posted by Mr Kong is now known as 'Cheryl's Birthday'

A school maths question posted on Facebook by a Singaporean TV presenter has stumped thousands, and left many asking if that's really what is expected of Singaporean students.

The question asks readers to guess the birthday of a girl called Cheryl using the minimal clues she gives to her friends, Albert and Bernard.

Cheryl's Birthday was initially reported to be an examination question for 11-year-olds.

Students stressed by tough examinations is a perennial issue here, and Cheryl's Birthday reignited concerns that the education system was too challenging.

Image source, facebook

But it later emerged it was for students aged about 15 taking part in last week's Singapore and Asian Schools Math Olympiads (Sasmo).

Organisers said the test was aimed at the top 40% and aimed to "sift out the better students", adding it was "important to clarify so that Singapore parents will not start to worry so much".

Image source, Twitter

Kenneth Kong, who first posted the problem, told the BBC: "It's a really difficult question for younger kids, so that's why people were so shocked at first... but now that people know it's for older students, they just think it's quirky."

Media caption,

Author and mathematician Alex Bellos demonstrates how to solve the problem

Sasmo's executive director Henry Ong defended the question, saying there was "a place for some kind of logical and analytical thinking in the workplace and in our daily lives".

Image source, Twitter

"We are not saying this problem is for every student... But if these kind of problems can be used to stretch the better students to sharpen their analytical power, why not?"

The question, which has been shared around the world, sparked a Twitter hashtag #cherylsbirthday and even a music track.

"After spending so much time together, thinking of Cheryl's birthdate, Albert and Bernard soon fell in love with each other and forgot all about Cheryl," said Elfy Bianca Hassan on Mr Kong's page.

"Dump her. Find other girls," suggested Nicholas Lim.

Image source, Twitter

Others took umbrage at the wording. "I hope people picked up that the person who set the question needs to go for English grammar classes - there are at least two grammar errors," said Clarence Singam-Zhou.

So when is Cheryl's birthday?

The answer is 16 July, said Sasmo which posted the correct solution.

Image source, Twitter

Sasmo also dismissed an "alternative solution" which resulted in 17 August.

Their rejection was that "since Bernard did not say that he does not know when Cheryl's birthday is, then how did Albert know that Bernard does not know?"

Problem solved.