Posted by Jose on Wednesday, November 7, 2012 at 9:24pm.
It would take them 70 minutes to wash the whole car working together, working at the same rate.
Jack did half the car by himself , and that would have taken him 70 minutes working alone
so that leaves half the car to be washed by both working together.
This will obviously take them 35 minutes.
so add 70 min + 35 min to 2:30 ----> 4:15 pm
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