Question

If a train takes $1$ second to cross a telegraph post and $3$ seconds to cross a platform $300$ metres long, then the length of the train (in metres) is

• A. $100$
• B. $150$
• C. $200$
• D. $300$

Answer 1

Answer: (B)

$150$

Length of train $=$ Speed of train $\times$ Time taken to cross the observer.

Length of train $+$ length of platform $=$ Speed of train $\times$ Time taken

Let the length of train be $x$m.

Let the speed of train be $y$m/s

$x=y⟶\left(1\right)$

$x+300=y\times 3$

$x+300=3x$

$x=150m$