A student walks to school at the rate of 7.5km/hr and reaches 10 minutes late.If he travels at the speed of 10km/hr he is 10 minutes early .What is the distance to the school?

The correct option is C

10km

Let the distance to the school be 1 km,then the time taken to cover 1km at the rate of 7.5km/hr=$\frac{distance}{speed}=\frac{1}{\frac{15}{2}}=\frac{2}{15}\times 60=8min$

Time taken to cover 1km at the rate of 10km/hr = $\frac{distance}{speed}=\frac{1}{10}=\frac{1}{10}\times 60=6min$

Difference in time taken = (8-6)=2min.

When the difference in time is 2min,the distance is 1km.

if the difference is 20min,the distance is $\frac{20}{2}=10km$