Two cars are start moving from the same point.

Let the starting point is .

After  hours, The first car is at point .

After  hours, The second car is at point .

Let the distance traveled by the first car is .

First car is travels at 60 mi/h.

Therefore, .

Let the distance traveled by the second car is b.

Second car is travels at 25 mi/h.

Therefore, .

Let the distance between the two cars at any time as .

Draw a right triangle with the given data :

After two hours,  and .

Solve  by using Pythagorean theorem to above figure.

The rate at which distance between two cars is increasing is .

Find  by differentiating  with respect to .

.

Differentiate on each side with respect to .

Substitute corresponding values in above equation.

.

The rate at which distance between two cars is increasing after two hours is           65 mi/h.

The rate at which distance between two cars is increasing after two hours is           65 mi/h.