Question

A Scooteriest goes to a place at a speed of 20 km per hour and return from there at a speed of 30 km per hour find the average speed in kilometre per hour for the entire journey

Answer 1

let the distance covered by the scooterist, when going to the place be x.  

while going v1 = x / t1   (where t1 is the time and v1 is velocity)

while returning v2 = x / t2  (where t2 is the time and v2 is velocity)

hence, t1 = x / 20,     t2 = x / 30

therefore , average speed  = total distance / total time

= 2x / x/20 + x/30   =   2x / 5x/60

= 2x * 60 / 50    =    24 km/h.