Correct Answer - Option 2 : 25 km

Let man covers x km distance by bus at a rate of 40 km/hr and (100 – x) km distance by scooter at a rate of 30 km/hr.

As we know,

Average speed = Total distance/Total time

32 = 100/ [(x/40) + {(100 – x) /30}]

32 = 100/ [(3x + 400 – 4x) /120]

32 (400 – x) = 100 × 120

400 – x = (100 × 120) /32 = 375

x = 400 – 375

x = 25 km