Question

A boat on a river travels 16 miles downstream in only 2 hours. It takes the same boat 7 hours to travel 28 miles upstream. What are the speed of the boat and the speed of the current?
speed of boat --- x mph
speed of current -- y mph

16/(x+y) = 2
2x + 2y = 16
x + y = 8

28/(x-y) = 7
7x - 7y = 28
x-y = 4

add them:
2x = 12
x = 6
then mentally y = 2

the speed of the boat is 6 mph, and the current is 2 mph

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