Two trains start from stations A and B and travel towards each other at the speeds of 60 km/h and 70 km/h respectively. At the time of their meeting, the second train has travelled 100 km more than the first. The distance between A and B is :

Correct option is B

Given:

Speed of Train A = 60 km/h

Speed of Train B = 70 km/h

At meeting point, Train B has travelled 100 km more than Train A

Concept Used:
If two objects move towards each other, the distance covered by each is proportional to their speeds. The difference in distances gives the required condition.

Solution:
Let time taken until meeting = t hours
Then:

Distance by Train A = 60t, Distance by Train B = 70t

Now,

70t - 60t = 100

10t = 100

t = 10

Distance by Train A = 60 × 10 = 600 km

Distance by Train B = 70 × 10 = 700 km

Total Distance = 600 + 700 = 1300 km 

Alternate Solution: ​

Time is constant. 

Speed ratio :       6     :      7

Distance ratio:   6     :      7 

7 - 6 = 100 

1 unit = 100 

Total distance = 6 + 7 = 13 $$\times 100 = 1300 \ km$$​​