Correct Answer - Option 3 : 20 km/hr

**Given:**

Reaches destination on time when speed = 40 km/hr

**Formula:**

Speed = distance/time

**Calculations:**

Let the time taken to reach the destination be 3x hours.

Total distance = 40 × 3x = 120x km

He covered 2/3 × 120x = 80x km in 1/3 × 3x = x hours

So, the remaining 40x km, he has to cover in 2x hours

Required speed = 40x/2x = 20 kmph

**∴ Required speed to reach destination on time is 20 km/hr**