Two trains of length 100 meters and 200 meters are 450 meters apart. They are moving towards each other on parallel tracks, at speeds of 90 km/h and 72 km/h. After how many seconds will the trains meet?  Choose the correct choice.
A) 6 B) 8 C) 10 D) 12 E) 14

Rationale: "the speeds are 90000 / 3600 = 25 m / s and 72000 / 3600 = 20 m / s the relative speed is 45 m / s . time = 450 / 45 = 10 seconds the answer is c ."
Answer: C