Question. A carpenter is building a house. He needs 80 woodblocks to build it. If he has 8 logs that can make five woodblocks each, how many logs does the carpenter still need?
Answer. 8
What step-by-step reasoning justifies that answer?
Reasoning: The carpenter initially has 8 x 5 = 40 blocks of wood. So he still lacks 80 - 40 = 40 blocks of wood. Therefore he still needs 40 / 5 = 8 logs of wood.