A man goes from place A to B at a speed of 12 km/h and returns from B to A at a speed of 18 km/h. His average speed for the entire journey is:

14.4 km/h 15 km/h 6 km/h 30 km/h

14.4 km/h

Average speed = \(\frac{2 × S1 × S2 }{S1 + S2}\) = \(\frac{2 × 12 × 18 }{12 + 18}\) = \(\frac{432 }{30}\) =   14.4 km/h