Boats & Streams

Ladakh Police Sub-Inspector · Mathematics · 20 practice questions with answers and explanations: 4 Easy, 16 Medium, 0 Hard.

Sample questions

Sample Easy question 1

A boat's speed in still water is 12 km/h and the stream flows at 4 km/h. Find its speed upstream.

  1. 8
  2. 3
  3. 16
  4. 12
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Answer: A. Upstream speed = boat − stream = 12 − 4 = 8 km/h.

Sample Easy question 2

A man rowing upstream against a 5 km/h stream moves at 10 km/h. What is his speed in still water?

  1. 5
  2. 20
  3. 15
  4. 10
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Answer: C. Upstream speed = x − 5 = 10, so x = 15 km/h.

Sample Easy question 3

A boat's speed in still water is 8 km/h and the stream flows at 2 km/h. How long will it take to travel 36 km upstream?

  1. 5 hours
  2. 4.5 hours
  3. 7.2 hours
  4. 6 hours
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Answer: D. Upstream speed = 8 − 2 = 6 km/h. Time = 36 ÷ 6 = 6 hours.

Sample Medium question 4

A boat goes 24 km downstream and returns the same distance upstream. If the speed of the boat in still water is 11 km/h and the speed of the stream is 5 km/h, find the total time taken for the round trip.

  1. 6 1/2 hours
  2. 4 4/11 hours
  3. 5 1/2 hours
  4. 5 hours
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Answer: C. Downstream speed = 16 km/h, upstream speed = 6 km/h. Time = 24/16 + 24/6 = 5 1/2 hours.

Sample Medium question 5

A boat goes 60 km downstream and returns the same distance upstream. If the speed of the boat in still water is 15 km/h and the speed of the stream is 5 km/h, find the total time taken for the round trip.

  1. 8 hours
  2. 10 hours
  3. 9 hours
  4. 8 1/2 hours
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Answer: C. Downstream speed = 20 km/h, upstream speed = 10 km/h. Time = 60/20 + 60/10 = 9 hours.

Sample Medium question 6

A boat goes 30 km downstream and returns the same distance upstream. If the speed of the boat in still water is 10 km/h and the speed of the stream is 5 km/h, find the total time taken for the round trip.

  1. 9 hours
  2. 8 hours
  3. 7 1/2 hours
  4. 6 hours
Show answer

Answer: B. Downstream speed = 15 km/h, upstream speed = 5 km/h. Time = 30/15 + 30/5 = 8 hours.

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