Mohan finishes a journey by scooter in 5 hours. He travels the first half of the journey at 30 km/h and the second half of the journey at 20 km/h. The distance covered by him is:

Let the total distance covered by Mohan = d

Time taken by Mohan to cover the first half = $$\frac{\frac{d}{2}}{30}$$ = $$\frac{d}{60}$$ hours

Time taken by Mohan to cover the second half = $$\frac{\frac{d}{2}}{20}$$ = $$\frac{d}{40}$$ hours

Total time for the journey = 5 hours

$$\Rightarrow$$ $$\frac{d}{60}+\frac{d}{40}=5$$

$$\Rightarrow$$ $$\frac{2d+3d}{120}=5$$

$$\Rightarrow$$ $$\frac{5d}{120}=5$$

$$\Rightarrow$$  d = 120 km

$$\therefore\ $$Distance covered by Mohan = 120 km

Hence, the correct answer is Option B