Multiple choice

A boat can travels 15km downstream in 18 min. The ratio of the boat in still water to speed of stream is 4:1. How much time will the boat take to cover 10km upstream?

  1. 22 minutes

  2. 25 minutes

  3. 20 minutes

  4. 30 minutes

  5. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Downstream speed = 15 km / (18/60) hr = 50 km/h. Boat speed : stream speed = 4:1, so boat speed = 40 km/h, stream speed = 10 km/h. Upstream speed = 40 - 10 = 30 km/h. Time for 10 km upstream = 10/30 hr = 20 minutes.

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