What would happen if the river flowed at 4…

What would happen if the river flowed at 4 km/h instead?

Question 33

MediumOriginal question

A swimmer swims at 4 km/h in still water. In a river flowing at 2 km/h, she swims 3 km downstream and then swims back to where she started.

What would happen if the river flowed at 4 km/h instead?

The round trip would take the same timeCorrect answerYour answerShe could not make any headway upstreamCorrect answerYour answerShe would get back in 3 hoursCorrect answerYour answerHer downstream time would doubleCorrect answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer B

Correct answer: B

Upstream speed would be $4 - 4 = 0$ km/h.
Swimming as hard as she can, she would only hold her place, so she could never swim back.

Concept: When the stream is as fast as the boat
Typical timeTypical: 120 s
Your timeYours: —

The rule this testsJourneys on a river

Practise this chapter →

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

Practise this chapter →

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

What would happen if the river flowed at 4 km/h instead?

Question 33

Explanation