Answer: Option A
$$\eqalign{
& {\text{Relative}}\,{\text{speed}} \cr
& = \left( {120 + 80} \right)\,{\text{km/hr}} \cr
& = {200 \times \frac{5}{{18}}} \,{\text{m/sec}} \cr
& = {\frac{{500}}{9}} \,{\text{m/sec}} \cr
& {\text{Let}}\,{\text{the}}\,{\text{length}}\,{\text{of}}\,{\text{the}}\,{\text{other}}\,{\text{train}}\,{\text{be}}\,{\text{x}}\,{\text{metres}}{\text{.}} \cr
& {\text{Then,}}\,\frac{{x + 270}}{9} = \frac{{500}}{9} \cr
& \Rightarrow x + 270 = 500 \cr
& \Rightarrow x = 230 \cr} $$