Question

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

Answer 1

D) 1.0 mph

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