If you ever rollerskate or rollerblade, you know how much fun it is to strap wheels to your feet. It’s like turning each foot into a car. But you probably haven’t tried to skate UNDER a car, much less 39 of them! A boy in Bangalore named Gagan Satish became famous because he can skate with his legs sticking straight out to the sides. He holds his ankles in his hands, and his face whizzes by just 5 inches above the ground! So he can scoot right under a parked car, and holds a record for zooming under a line-up of 39 of them. From these photos it doesn’t look comfortable, but it works for Gagan.
Wee ones: A roller skate wheel looks like a circle from the side. Try to find 4 circles in your room.
Little kids: If your roller skate has 2 wheels under your toe and 2 wheels under your heel, how many wheels does your foot have in total? Bonus: If you then skate like Gagan under 3 cars, how many wheels do those cars have? Count up by 4s if you can!
Big kids: If Gagan took exactly 2 seconds to pass under each car, how long would it take to skate under the row of 39 cars? Bonus: If he wanted to skate under 100 cars, how many more cars would he need in the lineup?
The sky’s the limit: If in the 39 car lineup, every 3rd car starting with the 3rd has the engine running, every 4th car starting with the 4th is really muddy, and every 5th car starting with the 5th is 2 inches lower than the rest, how many cars don’t give Gagan any extra trouble?
Wee ones: Items might include balls, buttons, the rim of a cup or plate, or the colored part of your eye (the iris)!
Little kids: 4 wheels. Bonus: 12 wheels.
Big kids: 78 seconds (1 minute 18 seconds). Bonus: 61 more cars.
The sky’s the limit: 16 cars offer no extra trouble. From 1 to 39 there are 13 multiples of 3, 9 multiples of 4, and 7 multiples of 5, or 29 cars. But there are some overlaps among those sets:
– 3 of the 4-multiples overlap with the 3-multiples (12, 24 and 36)
– 1 of the 4-multiples overlaps with the 5-multiples (20)
– 2 of the 5-multiples overlap with the 3-multiples (15 and 30)
So we have to subtract those 6 overlaps from the 29 cars to avoid double-counting, giving us just 23 troublesome cars. That leaves 16 cars with no issues. If you’d like to say which ones they are, they are cars #1, 2, 7, 11, 13, 14, 17, 19, 22, 23, 26, 29, 31, 34, 37, and 38.
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.