The train length of 700 metres is running at a speed of 72 km/hour. If this train crosses a tunnel in 1 minute, what is length of tunnel?
Correct Answer: Option C
Let the length of tunnel = x metres.
∴ Speed of train = \(\frac{{\left( {72 \times \frac{5}{{18}}} \right)m}}{s} = 20\;m/s\)
∴ Time \(= \frac{{700 + x}}{{20}}\) \(\left\{ {{\rm{time}} = \frac{{{\rm{distance}}}}{{{\rm{speed}}}}} \right\}\)
\(\Rightarrow {\rm{\;}}60 = \frac{{700 + x}}{{20}} \Rightarrow x = 500\)
Hence, the length of tunnel = 500 metres.
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