Puzzling over Cheryl’s birthday

I am a Singaporean and I have a confession – it took me a whole day to work out when Cheryl’s birthday was.

The Cheryl in question is, of course, the subject of the maths puzzle-turned-web sensation that has been stumping social media’s brightest and best over the past week.

First posted on Facebook by Singaporean television host Kenneth Kong, the puzzle was part of the Singapore and Asian Schools Maths Olympiad 2014, and was aimed at 15 and 16-year-olds. It has spawned numerous articles, a dedicated Wikipedia page, and even a (slightly bizarre) “math arpeggio” song which claims to depict the puzzle’s solution via the keys of an electronic piano (honestly).

Briefly, the puzzle features infuriating host Cheryl who refuses to specify when her birthday is, but instead tells friend Albert the month of her birthday and second friend Bernard (only) the day of the month, and gives them ten possible dates to choose from.

Trying to figure out Cheryl’s birthday was maddening. Not only is she incredibly vague to poor Albert and Bernard, but it was doubly goading because, like the dozens of teens that took part in Olympiad 2014, I too used to be a proud maths olympian back in the day.

Granted, this was only at primary school level, and most of the children in my class took part. Nobody really enjoyed them, and they faded into distant memories when I moved to England and started (wonderfully Olympiad-free) secondary school. But Cheryl and her infuriating birthday date has triggered a tiny, nagging worry that my maths prowess peaked at primary school and has been in steady decline ever since.

[Spoiler Alert] How the BBC solved it:

When I was at Singaporean primary school, maths puzzles such as this were like parody answers to a viral logic puzzle – ubiquitous. They followed very similar formats, all the way down to the imaginative trope of naming the characters in each problem according to the alphabet (Albert, Bernard, Cheryl – spot the pattern?). If there were four characters, their names were drawn from each of the four major ethnic groups that broadly make up Singapore (lChinese, Malay, Indian and Eurasian). All pretty formulaic for learning tools meant to stimulate creative problem-solving.

 It’s all Maths to me

“Singapore Maths” has acquired almost brand-like status in the United Kingdom, with tiger mothers rushing to find the best tuition centres and commenting online about which primary schools best incorporate it into their teaching methods. It has been lauded by educators for emphasising problem-solving skills and a deeper understanding of mathematical concepts from an early age, and was given the Gove stamp of approval in his changes to the British curriculum back when he was Education Secretary.

Of course, all these super-skills and accolades were completely lost on me and my fellow schoolmates puzzling over the daily slog of primary school classes. Maths involved a lot of puzzle-solving, but most memorably it also involved a lot of “model-making”. The idea is that instead of being faced with rows of symbols and numbers, it is a lot easier to grasp a mathematical concept by drawing out shapes (‘bars’) and visualising the maths problem that way. Students are meant to start off with concrete objects, drawing out the problem, before eventually progressing to solving problems in the abstract (i.e. with only numbers).

example of a bar model problem

Flickr: Roland O’Daniel


Logic puzzles and learning by model sound fun – but having to solve worksheets of ‘Cheryl’s birthday’ type puzzles every day is never going to be any child’s go-to activity of choice. Lots of friends actively hated it (one of them, upon hearing about this piece, immediately recalled her hatred of problem-based questions and that she sometimes used to cry when she got given a practise exam paper to do – “thank god I’m done with primary school maths classes!”).

Even Singapore’s parents, it seems, are finding the primary school maths curriculum tough going. Earlier this year it was reported by MyPaper that adults are now going for maths tuition “so that they can better understand what their children have to deal with in school”.

No wonder then that Cheryl’s birthday puzzle has intrigued so many people. It combines game-playing with a clever mix of emotional awe and frustration – “amazing, it’s meant for kids/it’s meant for kids, why can’t I do it?!”

For a smaller subsection of the web though, it also provoked incredulity that a brain-bending maths puzzle of the type that we thought we’d left behind at school could now be a crazy viral phenomenon. Problems like Cheryl’s birthday were par for the course when I was at school. Maybe it’s time for a new trend.

The latest new puzzle doing the rounds is the BBC Today’s programme’s one about prisoners and coloured hats. The primary school child in me is rolling her eyes; the other half of me is itching to waste another day having a crack at it.


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