A boat’s speed in still water is 22 km/h, while the river is flowing with a speed of 8 km/h and the time taken to cover a certain distance upstream is 4 hours more than the time taken to cover the same distance downstream. Find the distance.
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 105 km
Given that:
Still water speed = 22 km/h
Stream speed = 8 km/h
So,
Speed in upstream = (Still water's speed - Stream speed) = (22 - 8) = 14 km/h
Speed in downstream = (Still water speed + Stream speed ) = (22 + 8) = 30 km/h
According to the question:
The time taken to cover the upstream distance is 4 hours more than the downstream.
Let the required distance be x;
So,
[{x/(22 - 8)} - {x/(22 + 8)}] = 4
⇒ x/14 - x/30 = 4
⇒ (30x - 14x)/420 = 4
⇒ x = 420(4)/16
⇒ x = 105
Hence,
Distance = 105 km