The shuttle bus moved at a speed of 65 km / h for the first 3 hours, and then covered 140 km

The shuttle bus moved at a speed of 65 km / h for the first 3 hours, and then covered 140 km at a speed of 70 km / h. Determine the average speed of the bus on the route.

According to the conditions of the problem:

t1 = 3 hours – the time during which the bus covered the first section of the route;

V1 = 65 km / h – the speed at which the bus covered the first section of the route;

s2 = 140 km – the length of the second track section;

V2 = 70 km / h – the speed at which the bus was moving on the second section of the route.

It is required to find Vav – the average speed along the entire route (km / h).

Average speed is defined as the ratio of the total path to the time for which this path was covered:

Vav = S / t = (s1 + s2) / (t1 + t2) = (V1 * t1 + s2) / (t1 + s2 / V2) =

= (3 * 65 + 140) / (3 + 140/70) = (195 + 140) / (3 + 2) = 335/5 = 67 km / h.

Answer: The average speed is 67 km / h