Question

A train passes a telegraph post in $8$ seconds and a $264$ m long bridge in $20$ seconds. What is the length of the train?

• A. $170$ m
• B. $176$ m
• C. $164$ m
• D. $158$ m

Answer 1

Answer: (B)

$176$ m

Let the length of the train be $x$ metres and its speed by $y$ m/sec.
Since, $Distance=speed\times time$
$\therefore \frac{Distance}{speed}=time$
$\Rightarrow \frac{x}{y}=8\Rightarrow y=\frac{x}{8}$ .....(i)
and
$\Rightarrow \frac{x+264}{y}=20\Rightarrow x+264=20y$ ....(ii)
Now put $y=\frac{x}{8}$ in (ii). we get,
$\Rightarrow x+264=20\times \frac{x}{8}$
$\Rightarrow 8(x+264)=20x$
$\Rightarrow 8x+2112=20x$
$\Rightarrow 12x=2112$
$\Rightarrow x=176$
So, length of the train be $x=176$ metres
Option B is correct.