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Can you solve this maths problem that has everyone stumped?

It’s for high school students in Singapore.

Image: Shutterstock/gualtiero boffi

ARE YOU SMARTER than a very intelligent Singapore high school student?

That’s not a question you get everyday, but this maths puzzle, which was used during the Singapore and Asian Schools Math Olympiad on 12 April, has been melting heads across the internet.

Initially, people thought the question was a common-or-garden maths conundrum posed for ordinary students, but those who take part in the Olympiad are among the elite.

As the Singapore and Asian School Math Olympiads (SASMO) explained:

Being Question 24 out of 25 questions, this is a difficult question meant to sift out the better students. SASMO contests target the top 40% of the student population and the standards of most questions are just high enough to stretch the students.

It was meant for 15- and 16-year-old elite secondary school students, but swiftly went global after a local television news presenter posted it on his Facebook page.

Here’s the question:

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      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?


By yesterday, Internet users around the world were posting meticulously detailed answers to the puzzle on social media networks such as Facebook and Reddit.

The hashtag #cherylsbirthday also trended on Twitter, while some people created funny memes about the puzzle. 

Following relentless online debate about the question’s difficulty level, SASMO’s executive director Henry Ong issued another statement.

“We are pleased that this problem has generated so much interest and thinking from the public,” Ong said.
We are not saying this problem is for every student… but if this kind of problem can be used to stretch the better students to sharpen their analytical power, why not?

Want to know the answer? You’ll find it on the Olympiad’s Facebook page.

- With additional reporting AFP

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