A) 12 s
B) 15 s
C) 18 s
D) 20 s
Correct Answer: A
Solution :
When a train crosses a telegraph post, if covers its own length. \[\therefore \] Speed of first train \[=\frac{120}{10}=12\,\,\text{m/s}\] Speed of second train \[=\frac{120}{10}=8\,\,\text{m/s}\] Relative speed \[=12+8=20\,\,\text{m/s}\] Required time\[\text{=}\frac{\text{Total}\,\,\text{length}\,\,\text{of}\,\,\text{trains}}{\text{Relative}\,\,\text{speed}}\] \[=\frac{2\times 120}{20}=12\,\,\text{s}\]You need to login to perform this action.
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