Question

A boat can travel 54mph in still water. If it travels 124 miles with the current in the same length of time it travels 92 miles against the current, what is the speed of the current

Answer 1

8 mph

Explanation:

Let's say x is the speed of the current, and t is the time. When travelling with the current, the boat's speed is 54 + x. When travelling against the current, the boat's speed is 54 – x.

Distance = rate × time

124 = (54 + x) t

92 = (54 – x) t

Solve for t in each equation:

t = 124 / (54 + x)

t = 92 / (54 – x)

Set equal:

124 / (54 + x) = 92 / (54 – x)

Cross multiply:

124 (54 – x) = 92 (54 + x)

Distribute and solve:

6696 – 124x = 4968 + 92x

1728 = 216x

x = 8

The speed of the current is 8 mph.