Question

The average speed of a greyhound bus from lansing to detroit is 104.5 km/h. on the return trip from detroit to lansing the average speed is 56.2 km/h on the same road due to heavy traffic. what is the average speed of the bus for the round trip?

Answer 1

The average speed of the bus from Lansing to Detroit is 
$v_1 = 104.5 km/h$
while the average speed of the bus from Detroit to Lansing is
$v_2 =56.2 km/h$

The distance covered by the bus in the two trips is the same (the distance between the two cities), therefore, the average speed of the round trip can be calculated as the mean of the two speeds:
$v= \frac{v_1+v_2}{2}= \frac{104.5+56.2}{2}=80.35 km/h$