| A man standing on a platform finds that a train takes 3 s to pass him and another train of the same length moving in the opposite direction, takes 4 s. The time taken by the trains to pass each other will be |
A) \[2\frac{3}{7}s\]
B) \[3\frac{3}{7}s\]
C) \[4\frac{3}{7}s\]
D) \[5\frac{3}{7}s\]
Correct Answer: B
Solution :
| Let the length of each train be \[x\,\,m.\] |
| Then, speed of first train \[=\frac{x}{3}m/s\] |
| Similarly, speed of second train \[=\frac{x}{4}m/s\] |
| \[\therefore \]Relative speed \[=\frac{x}{3}+\frac{x}{4}=\frac{7x}{12}m/s\] |
| \[\text{Time}\,\,\text{taken}=\frac{\text{Distance}}{\text{Speed}}=\frac{2x}{\frac{7x}{12}}=\frac{24}{7}=3\frac{3}{7}s\] |
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