Just ZIP It

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.

Just ZIP It

August 13, 2014

When you mail a letter, you tell the post office where it’s going by writing the address: the street name and (building) number, the city, and the state. But big cities handling mail for lots of people have to split it into smaller batches, using ZIP (Zone Improvement Plan) codes. A ZIP code is a 5-digit number that says exactly which post office the mail should be sent to. A small town usually has just 1 ZIP code, but cities like New York or Houston have hundreds of them. And ZIP codes are pretty organized: they begin with 0 in the Northeast and get bigger as you head south and west, until you reach California ZIP codes that begin with 9. The President of the United States gets his very own ZIP code while in office, and Smokey Bear has his own code, too: kids sent him so many letters in the 1960’s, when ZIP codes were invented, that the post office gave him code 20252 all to himself. By the way, Smokey turns 70 this year, so feel free to send him a card!

Wee ones: Find out what your ZIP code is! Are any of the digits the same?

Little kids: Many ZIP codes are divided into even smaller areas using another 4-digit code after the 5-digit one. How many digits do those codes have in total?  Bonus: If the town next to yours has a ZIP code that’s just 1 more than yours, what would the next town’s code be? Find out your ZIP code to do this one!

Big kids: How many possible ZIP codes can America have given that the codes have 5 digits? Assume any slot can have any digit from 0 to 9.  Bonus: If Smokey turns 70 this year, in what year was Smokey “born”?




Wee ones: Different for everyone…ask a grown-up!

Little kids: 9 digits in total.  Bonus: Different for everyone…take your 5-digit ZIP code and add 1 to it as if it were a regular 5-digit number.

Big kids: 100,000, since there are 10 x 10 x 10 x 10 x 10 choices. Another way to think of it: there are 99,999 of them starting at 00001, plus 00000 itself.  Bonus: In 1944.

And if you do want to write to Smokey, his address is simply Smokey Bear, Washington, DC 20252. No street address needed because all 20252 mail goes to him!

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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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