Question

john covers a distance by driving a car at 60 kmphand he return back to the starting point on the scooter att 40kmph find the average speed for the whole journey

Answer 1

if any particle or body moves with V1 speed for some distance , and again particle moves backward same distance with speed V2 , then
average speed = 2V1V2/(V1 + V2)
here
V1 =60 km/h
and V2 = 40 km/h

so, average speed = 2×60×40/(60+40)
=4800/100 = 48 km/h

Answer 2

solution ;-

let we assume that the distance covered be 'x'

and the total distance be '2x'

therefore, the time that covers distance by john with his car be x/ 60

Now, the time taken to return with his scooter is x/40

so, the total time = (x/60) + (x/40) = 5x/120

Now, avg speed = total distance / total time
=2x/(5x/120)
=48km/hr.

hence, the avg speed for the whole journey is 48km/hr.