Multiple choice

A boatman can row his boat 2 km in 20 minutes against the stream and returns in 15 minutes. Then what is the speed of the boat in still water?

  1. 1 km/hr.

  2. 8 km/hr.

  3. 7 km/hr.

  4. 4 km/hr.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Upstream speed = 2 km / 20 min = 6 km/hr (boat - stream). Downstream speed = 2 km / 15 min = 8 km/hr (boat + stream). Let boat speed = b, stream speed = s. Then b - s = 6 and b + s = 8. Adding: 2b = 14, so b = 7 km/hr. Option C is correct.

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