A man travels from P to Q at the speed of 60 km/h and travels from Q to P at the speed of 90 km/h. What is the average speed of the man for the whole journey?
Answer & explanation
Correct answer: option 4
Average speed = \(\frac{ 2 × S1 × S2}{S1 + S2}\)
= \(\frac{ 2 × 60 × 90 }{60 + 90}\)
= = \(\frac{ 10800}{150}\)
= 72 km/h