A train takes 20 sec to cross a man who is standing on a platform . While it takes 25 sec to cross a 200 meter long platform . Find length of the train .
Answer & explanation
Correct answer: option 4
Let length of train = x meter
Time taken to cross a man is 20 sec . so total distance traveled is only length of train
Distance = Speed × Time
Speed = \(\frac{x}{20}\) ------ ( 1 )
Train takes 25 sec to cross a 200 meter long platform, total distance = 200 + x
Speed = \(\frac{200\;+\;x}{25}\) ---------- ( 2 )
Speed of train is same so put equation 1 equals to equation 2
\(\frac{x}{20}\) = \(\frac{200\;+\;x}{25}\)
25x = 4000+ 20x
5x = 4000 ⇒ x = 800 m
so, length of train = 800 m