A boat travels 12 miles downstream in 4 hours and returns upstream in 6 hours. Find the speed of the current and the speed of the boat in still water.
A) Boat: $2.5 \mathrm{mph}$; current: $0.5 \mathrm{mph}$
B) Boat: $0.5 \mathrm{mph}$; current: $2.5 \mathrm{mph}$
C) Boat: $5.5 \mathrm{mph}$; current: $3 \mathrm{mph}$
D) Boat: $3 \mathrm{mph}$; current: $0.5 \mathrm{mph}$

Question

Quizplus · Accepted Answer

The speed downstream is $12 \, \text{miles} / 4 \, \text{hours} = 3 \, \text{mph}$, and the speed upstream is $12 \, \text{miles} / 6 \, \text{hours} = 2 \, \text{mph}$. The boat's speed in still water is the average of these two speeds, $ (3 + 2) / 2 = 2.5 \, \text{mph}$, and the current's speed is the difference, $3 - 2.5 = 0.5 \, \text{mph}$.

A Boat Travels 12 Miles Downstream in 4 Hours and Returns