Multiple choice

Sunil can row a boat 20 km upstream in 1 hour 15 minutes. If the speed of the current of the river is 2 kmph, then how much time will it take to row the boat 30 km downstream?

  1. 1 h 10 m

  2. 1 h 45 m

  3. 1 h 30 m

  4. 1 h 20 m
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let boat speed in still water = b kmph. Upstream speed = b-2 covers 20km in 1.25 hours, so b-2 = 20/1.25 = 16 kmph, giving b = 18 kmph. Downstream speed = b+2 = 20 kmph. Time for 30km downstream = 30/20 = 1.5 hours = 1h 30m. Option A uses wrong speed. Option B adds time instead of calculating speed. Option D uses incorrect formula.

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