A boat moves at 10 km/h in still water, and the stream flows at 2 km/h. How long does it take to go 24 km downstream and come back?

2 hoursCorrect answerYour answer4.8 hoursCorrect answerYour answer5 hoursCorrect answerYour answer6 hoursCorrect answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer C

Correct answer: C

Down at 12 km/h: $\frac{24}{12} = 2$ hours. Back at 8 km/h: $\frac{24}{8} = 3$ hours.
Total 5 hours.

Worth noting

4.8 hours treats the water as still; the slow leg upstream costs more than the fast leg saves.

Ten questions from Boats & Streams, Pipes & Cisterns, at your own pace.

Ten questions from Boats & Streams, Pipes & Cisterns, at your own pace.

Explanation