Question

A man standing on a railway platform noticed that a train took $21$ seconds to cross the platform (this means the time elapsed from the moment the engine enters the platform till the last compartment leaves the platform) which is $88$ metres long, and that it took $9$ seconds to pass him. Assuming that the train was moving with uniform speed, what is the length of the train in metres?

• A. $55$
• B. $60$
• C. $66$
• D. $72$

Answer 1

The correct option is C $66$

Let length of the train be $x$ metres and speed be $s$.
Length of train + Length of platform $=x+88$
$\therefore s=\frac{x+88}{21}$
$\text{Also,}s=\frac{x}{9}$
$\Rightarrow \frac{x+88}{21}=\frac{x}{9}$
$\Rightarrow x=66$