Badri and Vasu are running at the same speed of 12 kms/hr. However, Badri started an hour earlier than Vasu. The distance between source and destination is 200 kms. After Vasu has covered 40 kms, he decides to increase his speed so that both of them reach the destination on time. By how much should Vasu increase his speed (in kms/hr)?

Correct option is D

Total time taken by Badri (who starts early):

​$$\text{Time}_{\text{Badri}} = \frac{200}{12} = 16.67 \text{ hours}$$

Vasu starts 1 hour later, so he must finish in:

$$\text{Time}_{\text{Vasu}} = 16.67 - 1 = 15.67 \text{ hours}$$

Vasu covers first 40 km at 12 km/h:

$$\text{Time for 40km} = \frac{40}{12} = 3.33 \text{ hours}$$

Remaining distance for Vasu:

$$\text{Remaining Distance} = 200 - 40 = 160 \text{ km}$$

​​​​​Remaining time for Vasu to finish:

​$$\text{Remaining Time} = 15.67 - 3.33 = 12.34 \text{ hours}$$

Required speed for remaining journey:

$$\text{Required Speed} = \frac{160}{12.34} \approx 12.97 \text{ km/hr}$$

​​​Speed increase needed:

​$$12.97 - 12 = 0.97 \text{ km/hr}$$​​