A Car covers a certain distance travelling at a speed of 30 km/h and returns to the starting point at a speed of 20 km/h.  Find the average speed of the car for the entire journey.

24

Average speed = \(\frac{2\;S_1\;S_2}{S_1\;+\;S_2}\)   .... (when Distance is same)

                      = \(\frac{2 × 30 × 20}{30 + 20}\) = 24 km/h