Question

Three trains A , B and C having speeds 50 km/hr , 20 km/hr and 70 km/hr respectively, if A and C move towards East and B moves towards west, then the ratio of relative speed of train A and B to the relative speed of train B and C?

1. 5 : 9
2. 9 : 7 
3. 5 : 2
4. 7 : 9
5. 4 : 5

Answer 1

Correct Answer - Option 4 : 7 : 9

Relative speed of train A and B = Speed_A + Speed_B 

⇒ 50 + 20 = 70 km/hr

Relative speed of train B and C = Speed_B + Speed_C

⇒ 20 + 70 = 90 km/hr

 ⇒ Required ratio = 70/90 = 7 : 9