Have you ever wondered how many sand particles it would 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: If your body has 6 square feet of skin, 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 dig out 10 cubic feet of sand, and then you 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?)
Answers:
Wee ones: You have more.
Little kids: 2 square feet, since your arms and legs take up 6. Bonus: 4 more square feet.
Big kids: 15 cubic feet. Bonus: 40 cubic feet. It would be just 20 cubic feet if you doubled in only one direction.
