Ram can row a boat in still water at the rate of 6 km/hr. He finds that it takes him twice as long to row upstream of a river as to row downstream of the same river, then the speed of the current of the river is
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 2 km/hr
Let the speed of the current be v km/hr. Then the upstream speed is \(6 - v\) and the downstream speed is \(6 + v\). For the same distance, time is inversely proportional to speed, so taking twice as long upstream means
\(6 + v = 2(6 - v)\)
\(6 + v = 12 - 2v\)
\(3v = 6\)
\(v = 2\)
So the speed of the current is 2 km/hr.
CBSE Applied Mathematics (Class XII):
Boats and Streams
