Tag Archives: number sense

So….When IS Cheryl’s Birthday???


I absolutely LOVE seeing a Singapore Math problem in the news! This challenging word problem taken from a recent Singapore and Asian School Math Olympiad (SASMO) contest has stumped people worldwide, and continues to go “viral” across the Internet. In case you haven’t yet seen it, the problem looks like this:

cheryl birthday

Now that you’ve probably read the problem several times over, how is it possible that a math problem contains no numbers other than the dates? The answer to that question is actually much more simple than the solution itself. Math doesn’t have to be limited to problems involving natural numbers or integers.

  • Math is about logic and reasoning.
  • Math is about creating order and patterns.
  • Math is about making sense of something that initially appears senseless.

Tackling problems like this can help children of all ages build number sense – a skill critical to mathematical achievement and success. But even more important, problems like this help to create the thought process required for rationalizing and finding solutions for problems that span subject areas and curricula. The satisfaction gained from attempting and ultimately solving these types of puzzles creates an attitude where “I don’t get it” is replaced with “let’s try another one!

So when IS Cheryl’s birthday? If you haven’t figured it out yet, watch the video below, courtesy of the BBC. And if you’re still not sure of how they came up with the answer, ask your kids. Chances are great that their exposure to Singapore Math strategies can make solving this problem easier than blowing out the candles on Cheryl’s birthday cake.

On the road….


The Posnack teaching abacus was spotted this morning at Starbucks! Our Abacus and Latte program is in full swing! Gather your friends or just join us yourself for a ten minute lesson on understanding how the abacus can strengthen your child’s understanding of place value and build strong number sense. We promise you will be an abacus maven before you’ve even finished your morning coffee.

To set up your own personal Abacus and Latte meeting, contact me at (jsilverman@posnackschool.org) or 954-583-6100 ext.604. abacus

If the answer is correct, why do I need to show my work?




Remember when it was enough to just come up with the right answer? While your teacher may have admonished you to “show your work,” credit was given simply based upon whether or not you got the correct answer to a given problem.  An algorithm was taught in Math class, you used that algorithm to work through several problems, and it didn’t matter if you really understood what you were doing as long as you memorized the necessary steps.

Fast-forward now to “Mathematics the Posnack Way” where the standards for demonstrating proficiency in Mathematics have changed. Research has shown that as a predictor of future mathematics success, a student’s understanding of a mathematical task is equally as important as his ability to demonstrate computational skills. But how do you know when your child “understands” a concept or idea? If your child can recite his multiplication tables without hesitation, isn’t he demonstrating proficiency in a valuable skill?

The answer is a resounding “YesANDNo!” Yes – your child has memorized an algorithm for finding the product of two numbers. This IS a necessary skill and will greatly benefit your child as he moves forward to higher levels of math. But does this ability to recite numbers based on rote memorization demonstrate a strong number sense? No – it does not. A strong number sense is not developed from memorizing facts or algorithms, but rather when children use learned strategies and an understanding of numerical relationships to solve problems.

At Posnack, our focus is on a problem-centered Mathematics curriculum. Students are encouraged to use manipulatives, drawings, games, and graphic representations to solve a variety of word problems. By discovering not just the “how” behind problem solving, but the “why” as well, your child will not only become a mathematical thinker, but will develop a life-long love and appreciation for Mathematics.

So what will your answer be the next time your child asks the question “Why do I need to show my work?” Before answering, consider this quote from Paul Lockhart, a mathematician, teacher, and author:

It is the story that matters, not just the ending.