Birthday Brainteaser

Most math riddles rattle your brain for a bit, but in the end, you are always able to find an answer. This math riddle, however, proved to be much too difficult, even for adults. Teacher Mr. Kong originally presented a riddled math problem to fifth graders in a Singapore classroom. The young children agonized over figuring out Cheryl’s birthday, trying to prove they “were way better at math than everyone else.” In truth, the math problem was actually from a math Olympiad test for high school students.

What is this mysterious advanced math problem, you ask? Well, it has to do with trying to find out Cheryl’s age! Here is what the problem was:


The math problem is not worded the best in the first place, but still is a math problem meant for mathematicians well beyond fifth graders.

The problem was eventually solved and explained through another article put out by the Times. This explanation looks at the dialogue exchanged back and forth between Albert and Bernard and the subtle indications that have been given based on the information that one man received and comparing it to dates and months that have multiple options. As you can see, there’s a lot more thought that has been poured into these responses even though they are extremely vague!

Try putting yourself to the test; do you think that you could fare with this classroom of fifth graders and figure out the math problem?

There are a lot of assumptions made in riddles, and a lot of “why?” questions. For example, if Bernard and Albert both claim that they know Cheryl’s birthday, why didn’t they just reveal their information instead of hiding their answer? Also, we must make an assumption that Albert and Bernard are actually telling the truth about knowing the answer. After working on these assumed truths, each exchange of dialogue brings the mathematician one step closer to Cheryl’s birthday by eliminating doubled options in different ways.

If you are interested in learning how to solve this math problem, you can read this follow up article about how to solve Cheryl’s birthday.


--Jessalyn Kieta

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