Question
Oliver and Justin take 2 days to assemble a toy train. Justin and Japheth take 4 days to build the same train while Oliver and Japheth take only 2 days. How many complete days would the three of them take to build the same toy train?
4 m

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Oliver and Justin take 2 days to assemble a toy train. Justin and Japheth take 4 days to build the same train while Oliver and Japheth take only 2 days. How many complete days would the three of them take to build the same toy train?