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Sam takes 20 days to build a wall.
Taylor and Kelly each take 10 days to build a wall.
How long will it take the three of them to build a wall if they work together?
Puzzle Copyright © Kevin Stone
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Answer
4 days.
Reasoning
In 20 days, Sam can build 1 wall, and Taylor and Kelly can each build 2 walls.
So, in 20 days, 5 walls can be built.
Therefore, one wall will take 4 days to build.