A third of the way, the motorcyclist was driving at a speed of 85 km / h. Then he reduced the speed to 15 km / h.

A third of the way, the motorcyclist was driving at a speed of 85 km / h. Then he reduced the speed to 15 km / h. How many hours did the motorcyclist take the rest of the way if he covered 420 km?

First, find 1/3 of the path that the motorcyclist traveled at a speed of 85 km / h. 420/3 = 140 km. In order to find the time during which the motorcyclist traveled this section of the path, you need to divide the distance by the speed: 140/85 = 1.6 hours. Now we will find the remaining distance that the motorcyclist covered at a speed of 15 km / h. 420 – 140 = 280 km. We find the time in the same way: 280/15 = 18.7 hours. The total path was: 1.6 + 18.7 = 20.2 hours.