A mountain road is 15 kilometers long. A car goes up the mountain 30 kilometers per hour, and goes down the mountain 50 kilometers per hour from the original road

A mountain road is 15 kilometers long. A car goes up the mountain 30 kilometers per hour, and goes down the mountain 50 kilometers per hour from the original road

2÷（1/30+1/50）
=2÷8/150
=37.5 km / h
or
（15+15）÷（15÷30+15÷50）
=30÷0.8
=37.5 km / h

There is a mountain road. When a car goes up the mountain, it is 40 kilometers per hour. When it goes back from the original road, it is 60 kilometers per hour when it goes down the mountain?

2÷﹙1／40+1／60）=48
The average speed of the car going up and down the mountain is 48 km / h