Question

Hi, I need help with this problem. I already know the answer (40mph) but I don't know how I solved it.

A boy leaves on a bicycle trip at the rate of 8 mph. One hour later the father, realizing that his son forgot his camping gear, sets out by car. How fast must the father drive to overtake the boy in 15 minutes?

Answer 1

Let's say the father does overtake the boy, the boy would have been travelling for 1 hour and 15 minutes at 8mph, therefor he would have travelled a total of 1.25*8 = 10 m
Now to reach the boy in 15 minutes the father must travel at a speed of 10/0.25 = 40 mph