When Maggie's friend got his notched stick, he said "This is great! Now, we need just one more piece!" He told Maggie that he needed a piece of clear plastic that was either a rectangle 4 inches on one side and 6 inches on the other or a square 5 inches on one side. "Either one will work," he said.
Maggie went to the hardware store with her mom. The man at the store said that clear plastic costs 50 cents per square inch. Maggie's mom said "Maggie, I think we should buy the square piece, because it costs less."
Was Maggie's mom right? What do you think the invention is now?
BONUS: How much would the cheapest piece cost?