Explanation:

Total length = 240+360 = 600 m

let speed of faster train X and slower’s Y (in m/s)

So,relative speed (while moving in opp. direction )= X + Y

and,relative speed (moving in same direction) = X - Y

1) crossed each other (moving in opp. direction) in 30 sec

distance traveled = 600 m

Relative speed = X + Y = 600/30 = 20 m/s…………………………………eq.1

2) crossed each other (moving in same direction) in [1 min + 40 sec] = 100 sec

distance traveled = 600 m

Relative speed = X - Y = 600/100 = 6 m/s…………………………………….eq.2

sloving 1 and 2

we get X = 13 m/s

Hence, option 2 is the correct answer.