Math problem

Question

A rowing team rowed 90 miles while going with the current in the same amount of time it took to row 10 miles against the current. The rate of the current was 4 miles per hour. Find the rate of the rowing team in still water.

Answer 1

x is speed of the boat

distance = rate * time

90 = (x+4) * t = xt + 4t

10 = (x-4) * t = xt - 4t

subtracting the equations:

80 = 4t - (-4t)

80 = 8t

t=10

It took them 10 hours one way....

per the second equation: 10 = (x-4)*10

1 = x-4

x =5

The speed of the boat is 5

With the current, the speed is 9 mph, which for 10 hours is 90 miles.

Against the current, the speed is 1 mph which for 10 hours is 10 miles

The speed is 5 mph, proven to be correct