The bus traveled for the first time 4 km in 12 minutes and the next 12 km in 15 minutes.

The bus traveled for the first time 4 km in 12 minutes and the next 12 km in 15 minutes. Find out the average speed of the bus along the way?

S1 = 4 km = 4000 m.

t1 = 12 min = 720 s.

S2 = 12 km = 12000 m.

t2 = 15 min = 900 s.

Vav -?

To find the average speed of movement Vav, it is necessary to divide the entire distance traveled by the train S by the time of its movement t along the entire path: Vav = S / t.

The travel time of the entire path is expressed by the sum: t = t1 + t2, where t1 is the time of movement on the first part of the path, t2 is the time of movement on the second part of the path.

t = 720s + 900s = 1620s.

The entire distance S will be the sum: S = S1 + S2, where S1 is the distance of the first section of the path, S2 is the distance of the second section of the path.

S = 4000 m + 12000 m = 16000 m.

Vav = 16000 m / 1620 s = 9.88 m / s.

Answer: the average bus speed was Vav = 9.88 m / s.