a) 230 m
b) 240 m
c) 260 m
d) 320 m
Answer: a
Explanation:
$$\eqalign{
& {\text{Relative}}\,{\text{speed}} = \left( {120 + 80} \right)\,{\text{km/hr}} \cr
& = {200 \times \frac{5}{{18}}} \,{\text{m/sec}} \cr
& = {\frac{{500}}{9}} \,{\text{m/sec}} \cr
& {\text{Let}}\,{\text{the}}\,{\text{length}}\,{\text{of}}\,{\text{the}}\,{\text{other}}\,{\text{train}}\,{\text{be}}\,{\text{x}}\,{\text{metres}}{\text{.}} \cr
& {\text{Then,}}\,\frac{{x + 270}}{9} = \frac{{500}}{9} \cr
& x + 270 = 500 \cr
& x = 230 \cr} $$
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