A motorboat crosses a certain distance in 1 hour and comes back in 1½ hours.…
2025
A motorboat crosses a certain distance in 1 hour and comes back in 1½ hours. If the stream is running at 3 km/h, find out the speed of motorboat in still water.
- A.
10 km/h
- B.
15 km/h
- C.
12 km/h
- D.
None of these
Attempted by 7 students.
Show answer & explanation
Correct answer: B
Answer:
15 km/h
Explanation:
Let the speed of motorboat in still water be x km/h. Then,
Downstream speed = (x + 3) km/h.
Upstream speed = (x – 3) km/h.
Then, (x + 3) × 1 = (x – 3) × 3/2
=> 2x + 6 = 3x – 9
=> x = 15.
So, the speed of motorboat in still water is 15 km/h.