Trunks, Teeth and Toenails

Trunks, Teeth and Toenails

September 22, 2015

Today is Elephant Appreciation Day, a day to celebrate all the cool things about elephants — including some amazing numbers behind those big gray bodies. First, there’s that amazing trunk, which has no bones but has 40,000 muscles! The trunk can suck up 10 gallons of water per minute. It also has two “fingers” at the tip that can grab and lift objects as heavy as 770 pounds. Then there are those giant feet: the distance around one foot is about 1/2 the elephant’s height. So if you measure a big footprint in the mud, you’ll know the size of the elephant was who made it! And finally even their toes are interesting: they have 5 toes on each foot, but on African elephants only 3 or 4 of those have toenails. Next time you see an elephant, check them out — but since elephants can weigh up to 6 tons, just make sure you don’t get stepped on.

Wee ones: Elephant tusks can grow up to 10 feet long! Who’s taller, you or that tusk? (Find out your height in feet!)

Little kids: If an elephant can suck up 10 gallons of water per minute, how much can it drink in 4 minutes? Count up by 10s!  Bonus: African elephants have 4 toenails on each front foot and 3 on each back foot. But Asian elephants have 5 on each front foot, 4 on each back foot. How many more toenails does an Asian elephant have?

Big kids: An elephant’s teeth include 12 premolars, 12 molars, and 2 tusks, which count as teeth too. How many teeth is that in total?  Bonus: An elephant can weigh up to 6 tons. That’s the same as how many 4,000-pound cars? (Reminder if needed: A ton equals 2,000 pounds.)

The sky’s the limit: If some people and some African elephants take a walk, and together they have 58 toenails, how many of each creature are walking? (Reminder: African elephants have 4 toenails per front foot and 3 per back foot. For the humans, count only their toenails, not fingernails.)




Wee ones: The tusk is definitely taller.

Little kids: 40 gallons: 10, 20, 30, 40.  Bonus: 4 more, since it has just 1 more per foot on each of 4 feet.

Big kids: 26 teeth.  Bonus: 3 cars! since it’s 12,000 pounds.

The sky’s the limit: 2 elephants and 3 people. Each human has 10 toenails, but each elephant has 14. So the multiple of elephant toenails has to end in 8 for the total to end in 8. So there must be either 2 or 7 elephants, and 7 would give us far too many toenails (98). That gives us just 2 elephants. Take away their 28 toenails and we’re left with 30, which must belong to 3 people.

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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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