Two trains 105 meters and 90 meters long, run at the speeds of 45 kmph and 72 kmph respectively, in opposite directions on parallel tracks. The time which they take to cross each other, is:

Two trains 105 meters and 90 meters long, run at the speeds of 45 kmph and 72 kmph respectively, in opposite directions on parallel tracks. The time which they take to cross each other, is: Correct Answer 6 seconds

Length of the 1^st train = 105 mLength of the 2^nd train = 90 mRelative speed of the trains,= 45 + 72 = 117 kmph= $$\frac{{117 \times 5}}{{18}}$$ = 32.5 m/secTime taken to cross each other,= $$\frac{{{\text{Length}}\,{\text{of}}\,{1^{{\text{st}}}}\,{\text{train}} + {\text{length of}}\,{2^{{\text{nd}}}}\,{\text{train}}}}{{{\text{relative }}\,{\text{speed }}\,{\text{of}}\,{\text{the }}\,{\text{trains}}}}$$∴ Time taken = $$\frac{{195}}{{32.5}}$$  = 6 secs.