When the wheel was invented thousands of years ago, that was just the beginning. Over hundreds of years people found all kinds of ways to use wheels, so now we have cars, trucks, bikes, and other ways to speed around. So of course, someone thought up the idea of sticking wheels right on our feet. On this day in 1869, Isaac Hodgson invented the roller skate (someone else had tried in 1760, but people just weren’t brave enough to try it). Now we have sports played entirely on skates, like roller hockey, speed skating and roller derby. All of these go faster on wheels, but are a lot harder than playing on your regular old feet.
Wee ones: What shape is a wheel? Try to spot 3 things in your room that are that same shape.
Little kids: A roller skate has 4 wheels. If you wear a pair of skates, how many wheels do you have? Bonus: If you skate by hanging onto the back of your car, how many wheels do you all have in total, including the steering wheel?
Big kids: Jeremy Strecker set the world record for jumping on skates over the most people lying on the floor. If each of the 11 people took up 20 inches of floor, how many inches did he jump? Bonus: Then there’s the world’s longest conga line on skates, where each skater hangs into the person in front of him. The longest line ever had 197 people. How many wheels did their skates have? (Hint: For a shortcut, figure it out for 200 people, then work your way down.)
The sky’s the limit: How many wheels does one skater-dog get to wear? And if you have a whole bunch of 4-skate skater dogs, could they have 132 wheels in total? (Hint: How can we tell whether a number is divisible by 2…then by 4…)
Wee ones: A circle. Other circles might includes buttons, the rim of a cup, and clocks.
Little kids: 8 wheels. Bonus: 13 wheels: 8 on your, 4 tires on the ground, and the steering wheel.
Big kids: 220 inches. Bonus: 1576 wheels. That’s 1600 (for 200 people) minus wheels for 3 people.
The sky’s the limit: Each dog has 16 wheels, and they can’t quite add up to 132. To be divisible by 16, a number has to be cut in half 4 times in a row. That brings us to 66, then 33…then we’re stuck. 128 is the closest workable number.
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.