Which of the following statements are true?
I. The speed in still water is the average of the downstream and upstream speeds.
II. The speed of the stream is half the difference of the downstream and upstream speeds.
III. A trip downstream and back takes the same time as the same distance in still water.
IV. For the same distance, going downstream takes less time than going upstream.

All four: I, II, III and IVCorrect answerYour answerI and II onlyCorrect answerYour answerI and IV onlyCorrect answerYour answerI, II and IV onlyCorrect answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer D

Correct answer: D

I and II come from $b + s$ and $b - s$ . IV: downstream is faster.
III is false: the round trip takes longer on a flowing river, since the slow leg upstream lasts longer.

Concept: Facts about boats and streams
Typical timeTypical: 120 s
Your timeYours: —

The rule this testsJourneys on a river

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

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