When You’re Stuck in the Sand

Now that it’s summer, our fan Sophia Y. asked, how many sand particles would it take to cover a person? First, there’s a grown-up formula to figure out how much area your skin covers! We tried it for a 50- pound, 42-inch tall kid, and got 8 1/2 square feet of skin area. Meanwhile it takes about 1 million grains to cover just 1 square foot. That’s just a thin layer…if you want a few inches of sand, you need hundreds of layers, giving us more than a billion grains! Luckily the beach has plenty of sand for the job. 

Wee ones: If your body has 7 square feet of skin and your friend has 5 square feet, who needs more sand to be totally covered?

Little kids: If your whole body has 8 square feet of skin, and each arm takes up 1 square foot of that and each leg takes up 2 square feet, what does that leave for your torso (the part in the middle)?  Bonus: How much more area would you need to reach 10 square feet?

Big kids: If you dig out 20 cubic feet of sand (imagine perfect cubes 1 foot wide), then shovel 8 cubic feet back into the hole, then dig out 4 cubic feet, then dump 1 cubic foot back in…how many cubic feet have you dug out in total?  Bonus: If you now make the hole twice as wide and twice as long (with same depth), how much sand have you dug out in total? (Hint if needed: What if you made it just twice as wide?)


Wee ones: You have more.

Little kids: 2 square feet, since your arms and legs take up 6.  Bonus: 2 more square feet.

Big kids: 15 cubic feet.  Bonus: 60 cubic feet. It would be just 30 cubic feet if you doubled in only one direction.


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