Multiple choice

The speed of a boat in still water is 7 km/hr and the speed of the stream is 3 km/hr. A man rows to a place at a distance of 60 km and comes back to the starting point. Find the total time taken by him?

  1. 17 hrs

  2. 20 hrs

  3. 21 hrs

  4. 15 hrs
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Downstream speed = 7 + 3 = 10 km/hr. Upstream speed = 7 - 3 = 4 km/hr. Time = (60 / 10) + (60 / 4) = 6 + 15 = 21 hours.

AI explanation

First, find the downstream speed by adding the boat's speed and the stream speed, which is 7 + 3 equals 10 km/hr, and the upstream speed by subtracting them, which is 7 - 3 equals 4 km/hr. Using the Time formula, the time to row to the place is 60 / 10 equals 6 hours, and the time to return is 60 / 4 equals 15 hours. Adding these times gives 6 + 15 equals 21 hours. The total time taken by him is 21 hrs.

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