Cheryl's Birthday: 'Primary 5' maths question turns out to be Sec 3 Math Olympiad question

Question, leaked from a contest, stumps netizens, sparks discussion online
By Amelia Teng and Jalelah Abu Baker, The Straits Times, 14 Apr 2015

A MIND-BOGGLING mathematics problem purportedly set as homework for a Primary 5 pupil turned out to be a question meant for upper secondary students taking part in high-level maths contests.

A photograph of the question, aimed at testing logical thinking, was posted by TV talk show presenter Kenneth Kong on Facebook on Saturday and was later shared almost 4,000 times. He told The Straits Times it was sent to him by a friend whose Primary 5 niece had asked him for help with an assignment last week.

It stumped netizens of all ages and sparked discussion on the use of such questions for pupils at any level.

More than 4,200 readers also shared the story through The Straits Times' Facebook page, with many exchanging solutions to the problem and expressing disbelief that Primary 5 pupils were expected to solve it.

Mr Henry Ong, founder of the Singapore and Asian Schools Math Olympiad, clarified that the question was from its contest for Secondary 3 and 4 students held last Wednesday. Students from more than 30 schools here took part in the competition. "This is a difficult question meant to sift out the better students, " he said in a reply to Mr Kong.

Mr Ong told The Straits Times yesterday that in his 10 years of organising such competitions for Primary 2 to Secondary 4 students, questions have never been leaked.

"We were very surprised because students were not allowed to keep their handphones on them," he said. The student who took the photo of the question is liable for disqualification from the competition, but he acknowledged that he or she would be hard to find.

The Ministry of Education told The Straits Times the question was not meant for Primary 5 pupils, who are around the age of 11.

"This question is not part of the Singapore primary or secondary mathematics syllabus," it said. "It is not reflective of the type of questions that are set in our mathematics assessments."

Parents and tutors agreed that the question did not test primary school maths concepts.

Mr Michael Tan, 46, a church worker who has a son in Primary 5, said: "It's fine if schools use them for fun and to challenge students, but these sort of questions should not be in exams."

Mr Tan Weiqiang, director of Junior Wonders Tuition Centre, said some schools may want to "stretch their brightest students" with such questions, but it is "very uncommon".

"This isn't what mainstream school students should be worrying about," said the former primary school maths teacher.

Mr Wallace Wong, a maths tutor and co-founder of tuition centre Study Room, said: "This isn't an examinable question but it could have been used to get kids thinking and interested in the subject. Sometimes, we provide puzzles like these for our students, to help them think out of the box, instead of the usual multiplication, division, fraction concepts."

Mr Zhou Shicai, who runs NickleBee Tutors, said: "It tests the child's comprehension and critical thinking skills, and his ability to apply logical thinking to an unfamiliar problem."

To whom it may concern,We would appreciate if you could post this reply to clarify the “supposedly P5 viral question”...
Posted by Singapore and Asian School Math Olympiads on Monday, April 13, 2015

THE SOLUTION

OUT of the 10 days, some numbers are repeated, only "18" and "19" are listed once.

If Cheryl's birthday happened on either of these two days, then Bernard (who was given the day but not the month) would have known immediately when it was.

As Albert is sure that Bernard can't possibly know the birthday yet, then her birthday cannot fall on the months where the "18" or "19" occur. So it can't happen in May or June, and must fall in July or August.

With this new information, Bernard can now pin down Cheryl's birthday for two reasons:

Two of the remaining five days are dated the 14th - as this number is repeated, it cannot be Bernard's choice, and they can both be ruled out.

With three remaining dates - July 16, Aug 15 and Aug 17 left, Bernard knows the correct date.

By this time, Albert (who was given only the month) also knows the birthday.

As there are two dates in August, Albert would be sure of the date only if Cheryl's birthday was in July.

Therefore, Cheryl's birthday is on July 16.

Source: Singapore and Asian Schools Math Olympiad

We would like to thank all those who wrote to us to suggest that there is an alternative answer to Q24 from the Sec 3...
Posted by Singapore and Asian School Math Olympiads on Monday, April 13, 2015

This question causes a debate with my wife .... and its a Sec 3 question. #trickquestion#cherylsbirthday
Posted by Kennethjianwen on Friday, April 10, 2015

Maths question catches world's attention
Newspapers, websites ask readers to solve problem set for S'pore teens
By Amelia Teng, The Straits Times, 15 Apr 2015

A PUZZLING question that tests upper secondary students' logical thinking skills in a mathematics contest here has taken the world by storm.

Several newspapers and websites around the world - from Britain and Malaysia to Canada and the United States - picked up the maths question and asked their readers to solve it.

The question, which had a photograph, was shared more than 4,500 times. The question gives 10 dates and asks students to figure out the birthday of a girl named Cheryl using limited information.

Some netizens had issues with the way the question was phrased and criticised the English used, while others made comments about Cheryl's coy behaviour.

The question was first posted by TV talk show presenter Kenneth Kong last Saturday. It stumped many netizens and prompted a rush of attempts online to try and tackle it.

The Singapore and Asian Schools Math Olympiads (SASMO), which set the question as part of its yearly contest, clarified on Monday that it was for Secondary 3 and 4 students.

Mr Kong had said he obtained the question from a friend whose Primary 5 niece had it as homework from her school.

British newspaper The Guardian said the question shows why Singapore comes out tops in international rankings in maths.

In the latest Programme for International Student Assessment, held in 2012, Singapore students came in second in maths, behind their peers in Shanghai.

Educators and publishers abroad now pay close attention to how maths is taught in Singapore - dubbed Singapore maths.

But the baffling question is not the toughest in maths contests here. Mr Henry Ong, founder of SASMO, said the contest, first held in 2006, was formed to give students a chance to try questions that are more manageable.

SASMO is meant for the top 40 per cent of primary and secondary schoolchildren. More than 28,000 contestants last week took part in the competition for primary and secondary schoolchildren. About 5,000 were from Singapore.

"The question highlighted was one of the top two most difficult questions in the test, but it would still be considered easy in the other competitions," he said, referring to contests held by the Singapore Mathematical Society (SMS).

An estate manager who took part in Olympiads in school said contests held by Raffles Institution, Hwa Chong Institution and the SMS are actually harder. Singapore is very well-regarded in the competitive maths scene, globally, he added.

Associate Professor Victor Tan, SMS' vice-president, said about half of the questions in a typical contest are "more challenging" than the regular maths curriculum, in order to sift out the best students.

A team of six is then chosen to represent Singapore at the International Mathematical Olympiad.

What's the 'problem'? Summing it up
The Straits Times, 15 Apr 2015

Dr Fong Ho Kheong, principal author of a series of maths textbooks used in primary schools here, said: "Even adults, at first glance, cannot solve this problem; they'll need some time. You have to study the relationship between the facts and use logical deduction to solve it."

"The international media picked up the question probably because they're also aware of Singapore maths," he said, adding: "They think that we emphasise this kind of question in our exams, and they equate it with our standing in maths."

But the question does not reflect Singapore's mainstream maths curriculum, he noted.

Associate Professor Manu Kapur from the National Institute of Education, who does maths education research, said questions found in Olympiad contests here and abroad are designed to be different from the curriculum.

"With some of these questions, it's not about knowing more. You still need to have maths knowledge, but it's about using what you know in a very creative way to solve problems," he said.

"Not all kids and adults are exposed to these sorts of questions."

People around the world have been trying to figure out Cheryl’s birthday (or at least wondering why she couldn’t she just save everyone a lot of trouble and be more direct with Albert and Bernard).
Posted by The New York Times on Tuesday, April 14, 2015