The car drove for 0.9 hours on a country road at 40 km / h and then another 0.6 hours on the highway.

The car drove for 0.9 hours on a country road at 40 km / h and then another 0.6 hours on the highway. How fast was the car driving on the highway, if its average speed along the entire path is 60 km / h?

Average speed is the ratio of the total distance traveled by a moving object to the total time that the object has spent on the entire journey.
1) 0.6 + 0.9 = 1.5 (hours) – there was a car on the road.
2) 60 * 1.5 = 90 (km) – the car has driven in total.
3) 40 * 0.9 = 36 (km) – the car drove at a speed of 40 km / h.
4) 90-36 = 54 (km) – the car drove 0.6 hours at an unknown speed.
5) 54 / 0.6 = 90 (km / h) – the speed of the car, with which it drove 0.6 hours.
Answer. 90 km / h.