A tour boat on a river travled 40 miles downstream in 4 hours. The return trip against the current took 5 hours.

What was the rate of the current?

A) 2.0 mph

B) 1.5 mph

C) 0.5 mph

D) 1.0 mph

D) 1.0 mph

Step-by-step explanation:

Own speed the boat = x

rate (speed) of the current = a

Speed of the boat downstream = (x + a)

Speed of the boat upstream = (x - a)

Speed of the boat downstream = 40 mi/4 h = 10 mi/h

Speed of the boat upstream = distance/time = 40 mi / 5 h = 8 mi/h

x + a = 10

x - a = 8

2x = 18

x = 9

x + a = 10

9 + a = 10

a = 1 mi/h