Correct Answer - Option 2 : 13.5 km/hr
Given:
The distance between L and M = 180 km
Formula used:
(Where S = The speed, D = The distance, and T = The time)
If A and B travel in opposite directions to each other then relative speed = (Speed of the A) + (Speed of the B)
If A and B travel in the same direction to each other then relative speed = (Speed of the A) - (Speed of the B)
Calculation:
Let us assume the speed of slower train be X
⇒ The speed of the faster train = X + 3
⇒
⇒ 12X + 18 = 180
⇒ 12X = 180 - 18
⇒ 12X = 162
⇒ X = 162/12 = 13.5 km/h
∴ The required result will be 13.5 km/h.