Question
Luke and David take 4 days to assemble a toy car. David and Fred take 4 days to build the same car while Luke and Fred take only 5 days. How many complete days would the three of them take to build the same toy car?
4 m

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Luke and David take 4 days to assemble a toy car. David and Fred take 4 days to build the same car while Luke and Fred take only 5 days. How many complete days would the three of them take to build the same toy car?