You know how roads have white and yellow lines painted down the middle? Those lines help cars drive straight so they don’t crash into each other. It might be one long line, or a line of dashes (lots of short pieces). How long do you think each dash is? Most people guess 2 to 3 feet, but they’re actually 10 feet long! Even more shocking is that they’re 30 feet apart. Because we look out ahead at dashes that are farther away, the dashes and the spaces between them look shorter than they are. Road lines were invented by accident in 1911, when a leaky milk wagon left a nice straight white trail on the street. Today’s machines drag a paintbrush along the road for just the right amount of time. But the driver has to drive very straight, or he’ll get some crazy-looking lines — and some bad driving.
Wee ones: Look around the room. What’s the longest straight line you see?
Little kids: If you press the button so the machine paints for 1 second, then leaves a space for 3 seconds, then paints for 1, then skips for 3, how long does that all take? Bonus: If you lay down next to one of these 10-foot road stripes, how much longer than you would it be? Find out your height in feet!
Big kids: If the 2nd dash you paint is all wiggly, then the 5th dash, then the 8th dash, what number dash is the 7th wiggly one? See if you can get it without counting! Bonus: A gallon of paint can make 180 feet of painted line. If you’re painting 10-foot-long dashes, how many dashes can you paint with 1 gallon?
Wee ones: Different for everyone…it might be a door frame, a stripe down a curtain, or the edge of the rug.
Little kids: 8 seconds. Bonus: Different for everyone again… subtract your height in feet from 10.
Big kids: The 20th, since each wiggly dash’s position is 1 less than 3 times its “wiggle count” (so the 7th is 1 less than 7 x 3). Bonus: 18 dashes.
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.