Have you ever seen someone chop a wooden board in half with her bare hand? Ouch! How do people do that? Well, for one thing, your bones are 40 times as hard as concrete. To top that off, even new karate students can move their hands at up to 13 miles an hour — and pros can reach 30 miles an hour, even smashing through cement blocks. Karate is a Japanese “martial art,” a sport where you use your arms, legs, and the rest of your body to protect yourself. Punching, kicking, and yes, those karate chops are all special skills you can learn. If you’d like to wow your friends, take those concrete bones and put them to work!
Wee ones: If you chop a wooden board, a cement block, and a small tree trunk, how many things did you karate chop?
Little kids: If you chop a board into 2 pieces, then chop each of those pieces into 2, how many little pieces do you have now? Bonus: If you break only every 3rd board you try, starting with the 3rd, what happens on the 9th board?
Big kids: If you chop at 20 feet per second, you can break a 1-inch thick board. But a black belt instructor can chop at 46 feet per second. How much faster is that? Bonus: If your hand is tough enough to break 1 board every 5 minutes, how many can you break in 1 hour if the first board breaks at 5 minutes? (Reminder if needed: An hour has 60 minutes.)
Wee ones: 3 things.
Little kids: 4 pieces. Bonus: You break it! 9 is a multiple of 3.
Big kids: 26 feet per second faster. Bonus: 12 boards, since there are 12 5-minute chunks in an hour.
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.