A train takes 5 seconds to pass an electric pole. If the length of the train is 120 metres, the time taken by it to cross a railway platform 180 metres long, is
1
\(12\frac{1}{2}\) seconds
2
\(7\frac{1}{2}\) seconds
3
\(6\frac{1}{2}\) seconds
4
\(3\frac{1}{2}\) seconds