Two stations P and Q are 200 km apart on a straight track. One train starts from P at 7 a.m. and travels towards Q at 20 kmph. Another train starts from Q at 8 a.m. and travels towards P at a speed of 25 kmph. At what time will they meet?  Choose the correct choice from the following choices
A) 10 am  B) 12 noon  C) 10.30 am  D) 12.30 am  E) 11 am

Rationale: "assume both trains meet after x hours after 7 am distance covered by train starting from p in x hours = 20 x km distance covered by train starting from q in ( x - 1 ) hours = 25 ( x - 1 ) total distance = 200 = > 20 x + 25 ( x - 1 ) = 200 = > 45 x = 225 = > x = 5 means , they meet after 5 hours after 7 am , ie , they meet at 12 noon answer is b ."
Answer: B