If a man takes 2 hrs either to row 7 km upstream or 15 km downstream, the speed of thecurrent in (kmph) is :

The correct answer is (b) 2.

Let $v$ be the speed of the boat in still water and $u$ be the speed of the current. The time it takes to row 7 km upstream is $7/(v-u)$, and the time it takes to row 15 km downstream is $15/(v+u)$. Since these times are equal, we have $7/(v-u) = 15/(v+u)$. Solving for $u$, we get $u = \frac{7v+15u}{15-7v} = \frac{7}{8}v$. The speed of the current is therefore $\frac{7}{8}$ of the speed of the boat in still water.

Option (a) is incorrect because it is the speed of the boat in still water, not the speed of the current. Option (c) is incorrect because it is twice the speed of the current. Option (d) is incorrect because it is four times the speed of the current.