Question

A motorcyclist drives from a to b with the uniform speed of 30 km/h-1 and returns back with the speed of 20 km/h-1.find the average speed?

Answer 1

let distance = x
total distance = 2x 

time = distance/speed
         = x/20 and x/30

total time =x/20 + x/30
              = 5x/60

average speed = total distance/total time taken 
                          = $\frac{2x}{5x/60}$
                          = 24km/hr