Time taken by Soma to drive one round of field in minutes, `a = 18`
Time taken by Ravi to drive one round of field in minutes, `b = 12`
In order to find the time when they meet again at the starting point, we have to find LCM of `a` and `b`.
`12 = 2^2**3 and 18 = 2^1**3^2`
`LCM(18,12) = 2^2**3^2 = 36`
So, after `36` minutes they will meet again at the starting point.