A man covered a certain distance at an average speed of 70 km/hr and comes back at the speed of 30 km/hr. Find the average speed (in km/hr) of the man during the whole journey?
Answer & explanation
Correct answer: option 3
Let speed of man while going = A
speed of man while coming back = B
Average speed = \(\frac{2 ×A × B }{A + B}\)
= \(\frac{2 ×70 × 30 }{70 + 30}\) = \(\frac{2 × 2100 }{100}\) = 42 km/hr