A man takes 50 minutes to cover a certain distance at a speed of 6 km/hr. If he walks with a speed of 10 km/hr, he covers the same distance in :

$$\eqalign{ & {\text{Distance}} = {\text{Speed}} \times {\text{Time}} \cr & {\text{Distance}} = \left( {6 \times \frac{{50}}{{60}}} \right){\text{km}} \cr & {\text{Distance}} = 5{\text{ km}} \cr & \therefore {\text{ Required time}} \cr & = \frac{{{\text{Distance}}}}{{{\text{Speed}}}} \cr & = \frac{5}{{10}}{\text{ hrs}} \cr & = \frac{1}{2}{\text{ hrs}} \cr & = {\text{30 min}} \cr} $$