What’s the last thing you’d expect to go viral? A math problem…yeah that’s what I thought too and I am happily surprised by how Cheryl’s Birthday, a math problem from Singapore, has spread like wildfire on the interwebs.
Here’s the basic problem:
Albert and Bernard just met Cheryl. “When’s your birthday?” Albert asked Cheryl.
Cheryl thought a second and said, “I’m not going to tell you, but I’ll give you some clues.” She wrote down a list of 10 dates:
May 15 — May 16 — May 19
June 17 — June 18
July 14 — July 16
August 14 — August 15 — August 17
“My birthday is one of these,” she said.
Then Cheryl whispered in Albert’s ear the month — and only the month — of her birthday. To Bernard, she whispered the day, and only the day.
“Can you figure it out now?” she asked Albert.
Albert: I don’t know when your birthday is, but I know Bernard doesn’t know, either.
Bernard: I didn’t know originally, but now I do.
Albert: Well, now I know, too!
When is Cheryl’s birthday?
That’s a doozy! While you’re thinking about it, let’s talk for moment about why love trying to figure it out (admit it you do!). Humans love finding answers. Think about it, when are you prouder than when you solve something whether it’s a rubix cube or world hunger?
As Daniel Bor, a research fellow at the University of Sussex in England and author of The Ravenous Brain: How the New Science of Consciousness Explains Our Insatiable Search for Meaning, explains in a Q&A with Time Magazine:
Human brains have an extreme form of consciousness: they’re ravenous for new innovative solutions to problems in the world, ravenous for optimizing our lives, for building pyramids of knowledge.
We want answers and going through the process of figuring things out makes us happy! That’s important to remember not only in our own lives, but also in our teaching. We don’t need to create a dog and pony show to make learning fun. Learning, real learning, is inherently enjoyable.
Not enjoyable like ice cream where every bite is better than the last, but enjoy like the enjoyment that comes after you finish a race or create a beautiful painting. It’s enjoyment that comes from putting in effort and doing something you are proud of – what Aristotle called eudaimonia, the highest human good.
So did you figure it out? Don’t cheat! Remember how guilty you felt when you looked at the back of the book before you gave a problem your best try? If you’re ready to check your work, here’s the answer and more importantly explanation in writing or via video.
One more quick note that I just couldn’t miss bringing up about Cheryl’s birthday. Yes, it’s a tough problem. Yes, Singapore is kicking the world’s butt in math right now and yes, there’s a ton we could discuss about that distinction. I’d be remiss, however, if I didn’t mention that this problem is a great example of why math need to go beyond worksheets and procedures. As The Atlantic reports:
So what makes Singapore so good at a subject with which America’s students have routinely struggled? Singapore’s math instruction focuses heavily on mastery over rote memorization. Math students on the small island nation perform well because they understand the material deeply—not because they are studying for a specific test. Thus, they react well when “curveballs” are thrown at them in the form of confusing math questions.
Furthermore, the instruction of “Singapore Math“—as it’s dubbed in the U.S. —uses a “layered” approach aimed at facilitating comprehension. Students digest the subject in stages, from the concrete to the pictorial and eventually to the abstract. This leads to conceptual understanding rather than numerical regurgitation: It’s not just about getting the correct answer, but also about explaining one’s thought processes.
Preach! Let’s give kids back the joy of figuring out math!