Question

A police car is located 60ft to the side of a straight road.

A red car is driving in the direction of the police car and is 90 ft up the road from the location of the police car. The police radar read that the distance between the red car and the police car is decreasing at a rate of 95 ft per second. How fast is the red car actually traveling along the road ?

Answer 1

If the red car is x feet away from the point of closest approach, then the distance z from the car to the cop is
z^2 = x^2 + 60^2
at x=90, z = 30√13
Now you have
z dz/dt = x dx/dt
so plug in your numbers