Two trains from opposite directions are to cross each other. The length of two trains are 100 meter and 200 meter respectively. The speed of first train is 100 km/hour and second train 200 km/hour. In how much time will they cross each other?	Choose the correct option:
A) 2 second
B) 3.6 second
C) 5 second
D) 5.5 second
E) 6 second

Rationale: the crossing moment starts when the head of first compartment of two trains meet or touch . the process of crossing each other continues till 100 + 200 meter = 300 meter is covered . the speed will be 100 km / hour + 200 km / hour = 300 km / hour . 300 x 1000 meter covered in 3600 seconds . so , 300 meter covered in 3.6 seconds . answer : b .
Answer: B