Boats & Streams

JKSSB Junior Engineer (Mechanical) · 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 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 Easy question 2

A boat's speed in still water is 15 km/h and the stream flows at 3 km/h. Find its speed downstream.

  1. 45
  2. 15
  3. 18
  4. 12
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Answer: C. Downstream speed = boat + stream = 15 + 3 = 18 km/h.

Sample Easy question 3

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 Medium question 4

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

Sample Medium question 5

A boat goes 48 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 3 km/h, find the total time taken for the round trip.

  1. 6 2/3 hours
  2. 6 1/6 hours
  3. 7 2/3 hours
  4. 6 2/5 hours
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Answer: A. Downstream speed = 18 km/h, upstream speed = 12 km/h. Time = 48/18 + 48/12 = 6 2/3 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 14 km/h and the speed of the stream is 4 km/h, find the total time taken for the round trip.

  1. 5 2/3 hours
  2. 4 2/3 hours
  3. 4 2/7 hours
  4. 4 1/6 hours
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Answer: B. Downstream speed = 18 km/h, upstream speed = 10 km/h. Time = 30/18 + 30/10 = 4 2/3 hours.

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