Today is Pi Day, and do you know why? If you cut a string that is the width of a circle, like a bike tire, you’ll need a little more than 3 of that string to wrap all the way around the edge. The exact number comes to 3.14159265…(it goes on and on). March 14, when written as 3/14, looks like the start of that number, so we have Pi Day. We use pi every day. As our friend Mary Claire A. shared, if you wrap a measuring tape around your head, find that length in inches, and divide by pi, you’ll get the width of your head — and that is your hat size! Better yet, when you bake a pie, the width tells you how much crust you’ll need around the edge…and that is the best pi of all.
Wee ones: Try to find 3 circles in your room.
Little kids: If you slice one pie into 6 slices and another same-size pie into 4 slices, which pie has bigger slices? Bonus: How many slices do the 2 pies have in total?
Big kids: If your bike has 2-foot-wide tires and they turn 10 times as you ride, about how many feet did you roll? (You can round pi to 3 if you like, or use 3 1/7, or try 3.14!). Bonus: If your head is 22 inches around, what hat size do you wear?
The sky’s the limit: If you ride 440 feet, how many times did the 2-foot-wide wheels turn, if you round pi to 3 1/7?
Wee ones: Answers might include clocks, edges of plates and cups, and Frisbees.
Little kids: The slices from the 4-slice pie are bigger: you cut fewer slices, so each has more pie in it. Bonus: 10 slices.
Big kids: The tire is about 6 feet around (or 6 1/7, or 6.28), so you ride about 60 feet (or 60 +20/7, which equals 62 6/7…or 62.8). Bonus: About size 7.
The sky’s the limit: 70 times. 2 x 3 1/7 (or 22/7) is 44/7, and if 440 is 44/7 of the wheel turn count, then 440 divided by 44 gives you 1/7 of it. 440/44 is 10. So 10 is 1/7 of the total turn count, giving us 70 turns.
Laura Bilodeau Overdeck is founder and president of Bedtime Math Foundation. Her goal is to make math as playful for kids as it was for her when she was a child. Her mom had Laura baking before she could walk, and her dad had her using power tools at a very unsafe age, measuring lengths, widths and angles in the process. Armed with this early love of numbers, Laura went on to get a BA in astrophysics from Princeton University, and an MBA from the Wharton School of Business; she continues to star-gaze today. Laura’s other interests include her three lively children, chocolate, extreme vehicles, and Lego Mindstorms.