7-Foot Shoe

Here's your nightly math! Just 5 quick minutes of number fun for kids and parents at home. Read a cool fun fact, followed by math riddles at different levels so everyone can jump in. Your kids will love you for it.

7-Foot Shoe

October 14, 2014

Yes, you’re seeing that picture right: it shows a man sitting inside a fuzzy, claw-shaped slipper. The slipper was a big accident, made wrong when Tom Boddingham tried to order one slipper in a different size from the other. His right foot is size 13, the left is 14 1/2. But when the factory in China saw the order for size 14.5, they misread it as size 145 and make him this roughly 7-foot-long furry footcover instead (the story reports them as making it size 1,450, but as you’ll see in the math below, that would have been even more enormous). Shoe sizes are a pretty messed-up measurement system to begin with: different countries use different sets of numbers, and none of them says exactly how long your foot is except in Korea. In America, each jump of 1 whole size makes the shoe 1/2 inch longer (so each half-size jump is 1/4 inch longer). Some people thought the company made the big slipper on purpose to get attention; either way, it clearly works well as a warm, fuzzy sleeping bag.

Wee ones: Are your two feet exactly the same length? Check them out sole to sole!

Little kids: If each fuzzy slipper has 4 claws on it, how many do they have together?  Bonus: If your foot was 3 inches long when you were born how much does it have to grow to become 3 times as long?

Big kids: If one of Tom’s feet is size 13 and the other is size 14 1/2, how many sizes apart are they?  Bonus: If a full size jump equals 1/2 inch more, how much longer in inches is his longer foot?

The sky’s the limit: A size 7 1/2 men’s shoe fits a 10-inch foot. If each full size jump is 1/2 inch and the factory misread the size as 145, exactly how big a foot can this slipper fit?

 

 

 

Answers:
Wee ones: Different for everyone…some people’s feet are different lengths, and either one can be longer!

Little kids: 8 claws.  Bonus: 6 inches.

Big kids: 1 1/2 sizes.  Bonus: 3/4 inch longer.

The sky’s the limit: 78 3/4 inches. If you’re counting from size 7 to 145, that jump of 138 sizes would match an increase of 69 inches. But we’re counting from 7 1/2, which is 1/4 inch longer to start, giving an increase of just 68 3/4 inches above a size 7 1/2. Added to the 10 inches, that gives us a 78 3/4 inch slipper — a little bit over 6 1/2 feet.

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About the Author

Laura Overdeck

Laura Overdeck

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 while still in diapers, 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.

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