Looking for classes? Ksquare Career Institute, Bengaluru →
A boat which has a speed of $5 km h^{-1}$ in still water crosses a river of width 1 km along the shortest possible path in 15 minutes. The velocity of the river water is
Explanation
$v = 1 km / ((1/4) h) = 4 km h^{-1}$ $v_{b} = 5 km h^{-1}$ $v_{w} = \sqrt{v_{b}^{2} - v^{2}} = \sqrt{25 - 16} = \sqrt{9} = 3kmh^{-1}$