Previous Year Questions

Here, 2 minutes = 2 * 60 seconds = 120 seconds

Then, 120 = (sum of lengths of train A and train B)/relative speed

From statement I: Speed of train A and train B is in the ratio 10: 9 respectively.

Then, speed of train A = (10/9) * speed of train B

From statement II: Train A and train B crosses a pole in 7.5 seconds and 5 seconds respectively.

7.5 = length of train A/speed of train A

Length of train A = 7.5 * speed of train A

And, 5 = length of train B/speed of train B

Length of train B = 5 * speed of train B

From statement I and II:

Length of train A = 7.5 *(10/9) * speed of train B

Length of train B = 5 * speed of train B

Since speed of train A is more than speed of train B and both the trains are moving in same direction. Then, relative speed = speed of train A - speed of train B

= (10/9) * speed of train B - speed of train B

= (1/9) * speed of train B

And, sum of length of both the trains = 7.5 *(10/9) * speed of train B + 5 * speed of train B

= (40/3) * speed of train B

Then, 120 = ((40/3) * speed of train B)/((1/9) * speed of train B)

From the above equation, speed of train B cannot be determined.

So, both statements I and II together are not sufficient to find the answer.