Every Wednesday I begin my math classes with a riddle. Most of them are math related and often have a connection to something we are studying or have studied. It is funny how similar they are to word problems but if I call it a “riddle” they instantly consider it a challenge worthy of their excited attention. Nearly all my collected riddles are not my own but come from riddle books or online sources. The riddle for my 7th and 8th graders today was the following:
“If 5 girls can sew 5 dresses in 5 days, how many girls would it take to sew 50 dresses in 50 days?”
I enjoy this riddle because there are number of mathematical ideas I can address regarding this one simple riddle. The solution to this riddle is obviously connected to ratios and proportions and can be an effective teaching moment for those concepts. More importantly though I make a point to emphasize the proper use of basic logic. It is remarkable how many students will answer 50. My response is always, why would I give this “riddle” to you if the answer is 50? This is mental laziness and will cause all kinds of problems if they allow it to find a place in their mental thinking. The final thing (related to the previous one) I try to emphasize is that often the point of a riddle is to be careful in trusting your intuition. Such riddles are fun because the answer seems so obvious but will contradict your original thought process. The student thinks “5, 5 and 5 in the first scenario so it must be 50, 50 and 50 for the second.” They correctly apply a pattern and they remember that Mr. Edwards is always saying “math is the science of patterns” so 50 must be the answer. Not in riddle land!
For the few out there reading this, if you would like a compilation of my collected riddles I would be more than willing to email you what I have.




