A swimmer swims at 5 km/h in still water, and the river flows at 1 km/h. What is the ratio of the time she takes to swim a distance upstream to the time she takes to swim it back downstream?

2 : 3Correct answerYour answer3 : 2Correct answerYour answer5 : 4Correct answerYour answer6 : 5Correct answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer B

Correct answer: B

Upstream speed $= 4$ km/h and downstream speed $= 6$ km/h.
For the same distance, time is inversely proportional to speed: upstream : downstream $= 6 : 4 = 3 : 2$ .

Worth noting

2 : 3 is the ratio of the speeds; the slower trip takes longer.

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

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

Explanation