Definition: You are given a math word problem and you are supposed to make use of mathematical concepts like probability, combinatorics, linear equations, sequences/series, or simple operators like addition, subtraction, division, or multiplication to answer the given question. Choose the best option from the 5 given options and report that option.
Input: Question: Two trains of length 100 m and 200 m are 100 m apart. They start moving towards each other on parallel tracks, at speeds 36 kmph and 72 kmph. After how much time will the trains meet?

 Option A: 10/3 sec

 Option B: 20/4 sec

 Option C: 20/7 sec

 Option D: 22/7 sec

 Option E: 60/7 sec

Option A