A young friend helped me test out these tube feet when I was working on Amazing Cardboard Tube Science. It’s the special extra experiment you get in the bind-up (a paperback with the whole series combined). He’s walking like a pro:

Challenge:

• Play with the materials used to make Tube Feet. Can you figure out the fewest number of tubes needed to hold you up? How much weight can each tube hold (assume your weight is being distributed evenly among the tubes)?
• Suppose you had a friend who weighed 70 pounds. Can you figure out how many tubes she would need to build Tube Feet?
• SuperDuper Challenge: Can you come up with a formula that would let someone use their weight to figure out how many tubes they need?
  • (Hint: Try starting with  “Number of Tubes =” and then use math symbols to describe how to figure out the number needed. You can use the phrase “your weight” to tell where to plug in how much the person weighs.

I would love to hear what you come up with!