The Truth about Toothpaste

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 Truth about Toothpaste

October 2, 2015

Brushing your teeth is kind of a weird activity, isn’t it? Who thought it up? Thousands of years ago, Babylonians and Egyptians used “chew sticks,” just twigs they pulled off trees to scrape their teeth. Then about 1,400 years ago the Chinese made a brush out of pig hairs shoved into a bamboo handle. Soon the Europeans tried horse hair instead — the bristles were softer, and who knows, maybe they tasted better, too. Meanwhile, back 2,000 years ago the Egyptians were also rubbing their teeth with a mix of rock salt, mint, ground up flowers, and pepper. The Romans were tough guys and decided to mix in crushed seashells and bones to scrub their teeth harder. For hundreds of years people tried mixing in charcoal, bread, and ashes from fireplaces. So no matter how you feel about brushing your teeth, you can be sure it tastes and feels better than in the old days!

Wee ones: If your toothpaste mixes salt, seashells, soot, bones and mint, how many ingredients in your tasty paste?

Little kids: If you brush your teeth every night starting Sunday but forget to on the 5th night, which night do you skip?  Bonus: If you brush twice a day, how many times do you brush in 1 full week?

Big kids: If you scrub your brush once tonight, 3 times the next night, 7 times the next, and 15 times the next, what number do you guess you brush the night after that?  Bonus: If the bristled brush showed up 1,400 years ago, around what year was that? (We’re in 2015 now.)




Wee ones: 5 ingredients.

Little kids: Thursday.  Bonus: 14 times, since a week has 7 days.

Big kids: 31 times, since you keep doubling the number you add: you add 2, 4, 8…then 16. Bonus:Around the year 615.

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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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