Two trains of equal length, running in opposite directions, pass a pole in 18 and 12 seconds. The trains will cross each other in?Options14.4 seconds15.5 seconds18.8 seconds20.2 seconds

To solve this problem, we first need to find the speed of each train.

1. Speed is calculated by dividing distance by time. In this case, the distance is the length of the train and the time is the time it takes to pass the pole.

2. For the first train, the speed is the length of the train divided by 18 seconds. We'll call this speed1.

3. For the second train, the speed is the length of the train divided by 12 seconds. We'll call this speed2.

4. When the two trains cross each other, they are effectively covering a distance equivalent to twice the length of one train (since both trains are of equal length).

5. The time it takes for the trains to cross each other is this total distance divided by the sum of their speeds.

Mathematically, this can be represented as:

Time = 2*(Length of train) / (speed1 + speed2)

Since the length of the train is the same for both, we can use the concept of relative speed here.

The relative speed of two objects moving in opposite directions is the sum of their individual speeds.

So, Time = 2*(Length of train) / (Length of train/18 + Length of train/12)

Solving this equation, we get Time = 2 / (1/18 + 1/12) = 14.4 seconds.

So, the trains will cross each other in 14.4 seconds. The correct option is 14.4 seconds.