Correct Answer - Option 3 : 48 kmph

**Given **

Speed of train in starting = 40 km/hr

**Formula Used **

Average speed = 2 × S_{1} × S_{2}/(S_{1} + S_{2})

**Calculation **

Speed of return journey = 40 + 40 × 50/100 = 60 km/hr

Average speed = 2 × 40 × 60/100 = 48 km/hr

**∴ The average speed of man is 48 km/hr **

This formula is used only when the distance covered is same for both cases.