Two trains start at the same time from A and B and proceed towards each other at speeds of 85 km per hour and 105 km per hour, respectively. When they meet, it is found that train from B has travelled 200 km more than the train from A. The distance between A and B is:

Correct option is D

​Given:

Train A's speed = 85 km/h

Train B's speed = 105 km/h

Distance difference = 200 km

Formula Used: 

If the time is constant,

$$\text{Relative speed ratio = Distance ratio}$$​​

Solution:

Ratio of speeds: 85 : 105 = 17 : 21 

​$$\text{Difference = } 21x - 17x = 200 \\ \ \\ \Rightarrow \quad 4x = 200 \\ \ \\ \Rightarrow \quad x = 50$$​​

Total distance:

​$$\text{Distance} = 17x + 21x \\ \ \\ = 38x = 38 \times 50 = 1900 \, \text{km}$$​​