Question

A bus goes A to B with 45km /h and return B to A with 85km/h , what is the average speed

Answer 1

$Averagespeed=\frac{TotalDistance}{Timetaken}.$
Let the distance between A and B be X km.
$Timetaken=\frac{Distance}{Speed}$
A to B time taken $=\frac{X}{45}$
B to A time taken $=\frac{X}{85}$
Total distance= 2X
$AverageSpeed=\frac{2X}{\left(\frac{X}{85}\right)+\left(\frac{X}{85}\right)}=58.85km/hr$