The speed of a boat in still water is 20 km/h, while the river is flowing at a speed of 8 km/h and the time taken to cover a certain distance upstream is 6 hour more than the time taken to cover the same distance downstream. Find the distance.
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 126 km.
Given that:
The speed of a boat in still water = 20 km/h
The speed of stream = 8 km/h
Let the distance be D km.
According to the question:
Downstream speed = 20 + 8 = 28 km/h
Upstream speed = 20 - 8 = 12 km/h
Now,
D/12 - D/28 = 6
⇒ D(7 - 3)/84 = 6
⇒ D = 6 × 84/4 = 126 km