The Secret to Our Streets

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.

The Secret to Our Streets

August 14, 2017

Did you know that our highways — the really big interstate ones — all follow a code? Look at the ones that stretch across the whole US: I-90 runs from Seattle to Boston, I-80 from northern California to New Jersey, and I-10 from southern California to Florida. Notice that all those numbers are even: east-west interstates get even numbers, and north-south ones get odds. The major ones are also multiples of 5, so those cross-country ones are multiples of 10. Better yet, the highways are lined up in numerical order. Small east-west numbers start way south in Florida, ending with I-90 and other high numbers way up north. I-5 in the West runs through Washington, Oregon and California, while I-95 runs down the East Coast. With over 46,000 miles of interstates, we need a good way to keep track.

Wee ones: If you were numbering interstates in order, what number would come after I-5?

Little kids: Can you name all the numbers from 1 to 10 that could be east-west (even) interstate numbers?  Bonus: Can you name all the multiples of 10 from I-10 to I-90?

Big kids: I-90 is the longest interstate at 3,020 miles, and the 2nd-longest is I-80 at about 2,900 miles. About how much longer is I-90?  Bonus: On the big highway signs for interstates, that little blue and red shield is 3 feet tall! It looks tiny only because it’s so high up. How much taller than that shield symbol are you, in inches?




Wee ones: I-6.

Little kids: They will be the even numbers: 2, 4, 6, 8, and 10.  Bonus: I-20, I-30, I-40, I-50, I-60, I-70, and I-80. But there’s no real I-50 or I-60, since they’d run right near the US highways with those numbers.

Big kids: 120 miles longer.  Bonus: Different for everyone… find your height in inches and subtract 36 inches, since that is 3 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 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.

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