question_answer

Two trains are \[2\,\,km\] apart their lengths are \[200\,\,m\] and \[300\,\,m\]. They are approaching towards each other with speed of \[20\,\,m/s\] and \[30\,\,m/s\] respectively. After how much time will they cross each other?

A) \[150\,\,s\]                        

B) \[100\,\,s\]

C) \[50\,\,s\]                                          

D) \[\frac{25}{3}s\]

Correct Answer: C

Solution :

Total distance travelled by two trains to cross each other                 \[=2000+300+200\]                 \[=2500\,\,m\] The total speed\[=20+30=50\,\,m/s\] \[\therefore \]  Time,\[t=\frac{\text{total}\,\,\text{distance}\,\,\text{travelled}}{\text{total}\,\,\text{speed}}\]                             \[=\frac{2500}{50}=50\,\,s\]