Question
Justin and Jeremy take 5 days to assemble a toy train. Jeremy and Mark take 4 days to build the same train while Justin and Mark take only 4 days. How many complete days would the three of them take to build the same toy train?
4 m

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Justin and Jeremy take 5 days to assemble a toy train. Jeremy and Mark take 4 days to build the same train while Justin and Mark take only 4 days. How many complete days would the three of them take to build the same toy train?