Multiple choice

Pramod rows a boat upstream a distance of 27 km in 3 hours and rows downstream a distance of 99 km in 3 hours. What is the sum of the total time taken if Pramod rows a distance of 42 km in still water and a distance of 66 km downstream?

  1. 2

  2. 3

  3. 5

  4. 4

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

Let boat speed = b, stream speed = s. Upstream speed = b - s = 27/3 = 9 km/h. Downstream speed = b + s = 99/3 = 33 km/h. Solving: b = (9+33)/2 = 21 km/h, s = (33-9)/2 = 12 km/h. Time to row 42 km in still water = 42/21 = 2 hours. Time to row 66 km downstream = 66/33 = 2 hours. Total time = 2 + 2 = 4 hours.

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