Speed Time Distance Questions - Boats, streams : Ascent Education - CAT, XAT Entrance Coaching Classes

Question 4 the day: April 22, 2003
The question for the day is from the topic Speed, Time and Distance and helps understand the concept of Boats in Streams.

Question
The speed of a motor boat itself is 20 km/h and the rate of flow of the river is 4 km/h. Moving with the stream the boat went 120 km. What distance will the boat cover during the same time going against the stream?

1. 80
2. 180
3. 60
4. 100

Correct Answer is 80. Choice (1) is right.

Explanatory Answer

Let the distance to be covered by the boat when it is travelling against the stream be x.

The boat goes down the river at a speed of 20 + 4 = 24 km/h and up the river at a speed of 20 - 4 = 16 km/h.

Since the time taken is same 120/24 = x/16
Therefore, x = 80 km.

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