Say \(L\) is the length of the train.
Speed of the train \(=45 \mathrm{~km} / \mathrm{hr}=45 \times(5 / 18) \mathrm{m} / \mathrm{s}=12.5 \mathrm{~m} / \mathrm{s}\)
Time taken by the train to cross the platform i.e. travel the distance \((L+100) m\) is 60 seconds.
\(\Rightarrow(L+100) / 12.5=60 \quad[\) Distance \(/\) speed \(=\) Time \(]\)
\(\Rightarrow(L+100)=60 \times 12.5=750\)
\(\Rightarrow \mathrm{L}=650 \mathrm{~m}\)
\(\therefore\) Time taken to cross an electric pole \(=(650 / 12.5)\) seconds \(=52\) seconds