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 speed of current = $v$ km/hr.
Speed upstream = $6 - v$
Speed downstream = $6 + v$
Given:
Time upstream = 2 × Time downstream
Since time = $\frac{d}{\text{speed}}$ and distance is same:
$\frac{1}{6 - v} = 2 \cdot \frac{1}{6 + v}$
Cross-multiply:
$6 + v = 2(6 - v)$
$6 + v = 12 - 2v$
$3v = 6$
$v = 2$
The speed of the current is 2 km/hr.