What is the average speed of the train if it covered the first third of the track at a speed of 30 m / s, the second

What is the average speed of the train if it covered the first third of the track at a speed of 30 m / s, the second third at a speed of 20 m / s, and the last part of the track at a speed twice the average speed on the first two sections of the track?

Since the entire track is divided into equal sections (1/3 of the distance), the average train speed on the first and second sections of the track will be:

(20 + 30) / 2 = 50/2 = 25 m / s;

The train will pass the last part of the journey at a speed:

25 * 2 = 50 m / s;

Thus, the average speed of the train along the entire route will be:

(20 + 30 + 50) / 3 = 100/3 = 33 1/3 = 33.3333 … = 33, (3).