Question

A motorboat heads upstream a certain distance and returns to its starting point. The trip up and back

takes 9 hours. The current is running at 5 miles per hour (mph). If the motorboat maintained a constant
speed of 10 mph relative to the water, what is the total distance of the trip?

Answer 1

67.5 miles

Explanation:

If x is the distance one way, then the time it takes when moving with the current is:

x = 15 t₁

The time it takes when moving against the current is:

x = 5 t₂

The total time is 9 hours:

t₁ + t₂ = 9

Substituting:

x/15 + x/5 = 9

4x/15 = 9

4x = 135

2x = 67.5

The total distance round trip is 67.5 miles.