Driving along the highway, the motorcyclist drove 900m at a speed of 15 meters per second and then

Driving along the highway, the motorcyclist drove 900m at a speed of 15 meters per second and then on a bad road drove 400 meters at a speed of 10 meters per second. At what average speed did he go all the way?

Average vehicle speed over the entire journey:

Vav. = S / t, where S is the entire distance covered (S = S1 + S2), t is the time of movement (t = t1 + t2).

Car driving on the highway:

S1 = 900 m, t1 = S1 / V1, where V1 = 15 m / s.

Driving on a bad road:

S2 = 400 m, t2 = S2 / V2, where V2 = 10 m / s.

Vav. = (S1 + S2) / (S1 / V1 + S2 / V2).

Let’s perform the calculation:

Vav. = (900 + 400) / (900/15 + 400/10) = 1300/100 = 13 m / s.

Answer: The car drove all the way at an average speed of 13 m / s.