A car travels a certain distance with a speed of 50 km/hr and returns with a speed of 40 km/hr. Calculate the averagespeed for whole journey.

Suppose distance between the points (let say A and B)=x m

 then total distance travelled by the car =x+x=2x m

Going from A to B,

Speed of the car=50 km/h

so time=x/50 hours

Returning back from B to A,

speed of the car=40 km/hour

So time=x/40 hours

Average speed for the whole journey=total distance/total time

=