Given: A car travels from A to B at a speed of 40km∕hr Travels back from B to A at a speed of 30km∕hr And again goes from A to B at a speed of 60km∕hr Formula Used: Speed = Distance ∕ Time Average speed = Total distance/Total time Calculation: Let the distance between A and B is dkm According to the question Total distance =d+d+d=3d Total time =
d
40
+
d
30
+
d
60
Now, Average speed =
3d
d
40
+
d
30
+
d
60
⇒
3d
3d+4d+2d
120
=
3d×120
9d
=40km∕hr ∴ The average speed of car in the whole journey is 40km∕hr.