If a man goes from place A to B at a speed of 12 km/h and return at a speed of 18 km/h, then the average speed for the whole journey is:
Answer & explanation
Correct answer: option 3
Average speed = \(\frac{2 × S1 × S2 }{S1 + S2}\)
= \(\frac{2 × 12 × 18 }{12 + 18}\)
= \(\frac{432 }{30}\)
= 14\(\frac{2 }{5}\) km/h