A boat can move 5 km/hr in still water. If the river is running at 1 km/hr, it takes it 75 min to move to a place and back. How far is the place?

Let the place be at a distance of 'd' kms

From the given data,

$\frac{d}{5 - 1} + \frac{d}{5 + 1} = \frac{75}{60} \mathrm{kms}\frac{d}{4} + \frac{d}{6} = \frac{5}{4}$

5d/12 = 5/4 => d = 3 kms.

Hence, the place is 3 kms far.