The bus traveled once 4 km at an average speed of 20 km / h, the next 12 km at an average speed of 40 km / h.

The bus traveled once 4 km at an average speed of 20 km / h, the next 12 km at an average speed of 40 km / h. What is the average speed of the bus along the entire route?

Average speed:
Vav. = S / t, where S is the total distance traveled (S = S1 + S2, where S1 = 4 km, S2 = 12 km), t is the total travel time (t = t1 + t2).
Travel time when passing sections of the path S1 and S2:
t1 = S1 / V1, where V1 = 20 km / h.
t2 = S2 / V2, where V2 = 40 km / h.
Let’s calculate the average speed of the bus:
Vav. = (S1 + S2) / (t1 + t2) = (S1 + S2) / (S1 / V1 + S2 / V2) = (4 + 12) / (4/20 + 12/40) = 16 / 0.5 = 32 km / h.
Answer: The average speed of the bus is 32 km / h.