Correct Answer - Option 2 : 110 sec

**GIVEN:**

Length of Train = 250 meter.

Length of Platform : Length of Train = 3x : 1x

Length of Platform = 750 meter.

Speed of train B = 54 kmph or 15 m/s

**ASSUMPTION:**

Let the time taken to cross each other = T seconds.

Let speed of Train A = (S) m/s.

**FORMULA USED:**

Speed of Train = length of Train / Time taken ----(1)

**CALCULATION:**

From eq(1)

⇒ S = (750 + 250) / 50

⇒ S = 20 m/s or 72 kmph

When Train A and B cross each other.

⇒ (v - v_{B}) = (250 + 300)/T

⇒ T = (250 + 300)/5

⇒ Time = 110 seconds.