A boat covers a certain distance downstream in 1 hour, while it comes back in…
2025
A boat covers a certain distance downstream in 1 hour, while it comes back in 1 1/2 hours. If the speed of the stream be 3 kmph, what is the speed of the boat in still water?
- A.
15 kmph
- B.
13 kmph
- C.
10 kmph
- D.
None of these
Attempted by 5 students.
Show answer & explanation
Correct answer: A
Solution: Let the speed of the boat in still water be x kmph.
Speed downstream = x + 3 kmph; Speed upstream = x - 3 kmph.
The distance covered is the same both ways. Time downstream = 1 hour and time upstream = 1.5 hours. Therefore:
(x + 3) × 1 = (x - 3) × 1.5
Expand: x + 3 = 1.5x - 4.5
Rearrange: x - 1.5x = -4.5 - 3 ⇒ -0.5x = -7.5
Solve: x = (-7.5)/(-0.5) = 15
Therefore the speed of the boat in still water is 15 kmph.