Who invented brushing your teeth? Thousands of years ago, Babylonians and Egyptians used “chew sticks,” scraping their teeth with tree twigs. Then about 1,400 years ago the Chinese made a brush out of pig hairs in a bamboo handle, while Europeans tried horse hair. Meanwhile, the Egyptians were also rubbing their teeth with a mix of rock salt, mint, ground up flowers, and pepper. The Romans mixed in crushed seashells and bones. So you can be sure brushing your teeth 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 brush 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 2022 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 622.
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.