How many teeth are out there in the world? Well, of the 8 billion people out there, about 7 billion have their final 28 teeth, or 32 with wisdom teeth. Let’s call it 30 – that gives us 210 billion teeth. Then if about 1 billion kids still growing teeth have 10 each, that’s another 10 billion. But what about all our toothy animal friends – dogs, cats, beavers, raccoons…and sharks, who have 50-100 teeth at any time. There are trillions of teeth out there – and probably not enough toothbrushes!
Wee ones: Look in a mirror. How many teeth can you see? Count as many as you can!
Little kids: If you have 4 teeth on top and 4 teeth on the bottom facing them, how many teeth do you have? Bonus: If you then lose 2 teeth, grow 3 more teeth, lose another tooth, and then grow 2 more, how many teeth do you have now?
Big kids: If there are 210 billion grown-up teeth out there and 10 billion kid teeth, how many teeth is that? Bonus: If you start with 2 teeth and end up with 32 teeth, how many times does your number of teeth double?
The sky’s the limit: If at a party every kid has 10 teeth and every grown-up has 28, how many of each must you have if there are 114 teeth in the room?
Answers:
Wee ones: Different for everyone…see how many you can count!
Little kids: 8 teeth. Bonus: 10 teeth.
Big kids: 220 billion teeth. Bonus: 4 times: to 4 teeth, then 8, then 16, then 32.
The sky’s the limit: 3 kids and 3 grown-ups. Since the numbers ends in 4, and since kid teeth don’t affect the last digit (we keep adding 10), we need 3 grown-ups to give us 84 grown-up teeth. Then we need 3 more kids to add the 30 to get us to 114.
