Question

Find the average speed of a car moving from point a to b with speed 30km/h and return speed is 40km/h

Answer 1

Average speed=Total speed/total time taken

Or avg. speed=total speed/number of sppeds

=30km/h+40km/h divided by 2

:.35km/h Ans

Answer 2

From a to b,

speed=30km/hr

distance=s

time=distance÷speed

=s/30

From b to a,

speed=40km/hr

distance=s

time=distance÷speed

=s/40

Av.speed=total distace/total time

=s+s/(s/30)+(s/40)

=2s/(7s/120)

=240/7

=34.28km/hr

Hope it helps