If A travels to his school from his house at the speed of 3 km/h, then he reaches the school 5 minutes late. If he travels at the speed of 4 km/h, he reaches the school 5 minutes earlier than school time. The distance of his school from his house is:

Explanation:-

Let the distance between school and home be x km.
The difference of time when A goes school to school with these two different speed is 10 min $$\eqalign{ & = \frac{{10}}{{60}}\,{\text{hour}} \cr & {\text{Now,}} \cr & \left( {\frac{x}{3}} \right) - \left( {\frac{x}{4}} \right) = \frac{{10}}{{60}} \cr & {\text{Or}},\,\frac{x}{{12}} = \frac{1}{6} \cr & {\text{Or}},\,x = \frac{{12}}{6} \cr & = 2\,{\text{km}} \cr}$$