A speedboat runs 6 km upstream in a river and comes back to the starting point in 33 minutes. The stream of the river is running at 2 km/hr. What is the speed of speedboat in still water?**(A)** 25 km/h**(B)** 21 km/h**(C)** 26 km/h**(D)** 22 km/h**Answer:** **(D)****Explanation:** Let the speed of speedboat in still water be x km/h.

Then, speed downstream = (x + 2) km/h, speed upstream = (x – 2) km/h.

Since it goes 6 km upstream and comes back in 33 minutes, we have

6/(x+2) + 6/(x-2) = 33/60

⇒ 11x² – 240x – 44 = 0

⇒ 11x² – 242x + 2x – 44 = 0

⇒ (x – 22)(11x + 2) = 0

⇒ x = 22.

Therefore, the required speed = 22 km/h.

Quiz of this Question

Please comment below if you find anything wrong in the above post

DSA Self Paced Course

View Details