A boat can maintain a constant speed of 34 mph relative to the water. The boat makes a trip upstream to a certain point in 21 minutes; the return trip takes 13 minutes. What is the speed of the current?

Answer 1

Distance = rate * time

Let x = speed of current

rate upstream = 34 - x

rate downstream = 34 + x

21(34 - x) = 13(34 + x)

Solve for x.