Question. Josh wants to build a square sandbox that is 3 ft long, 3 ft wide for his son. He can buy sand in 3 sq ft bags for $4.00 a bag. How much will it cost him to fill up the sandbox?
Answer. 12
What step-by-step reasoning justifies that answer?
Reasoning: The sandbox is 3' long, 3' wide so the sq footage of the sandbox is 3 * 3 = 9 sq ft. He needs 9 sq ft of sand to fill the sandbox and he can buy it in 3 sq ft bags so he needs 9 / 3 = 3 bags of sand. The sand costs $4.00 a bag and he needs 3 bags so it will cost him 4 * 3 = $12.00 in sand.