Miscellaneous Question 24
- At $60 \%$ of its usual speed, a train of length L metres crosses a platform 240 metre long in 15 seconds. At its usual speed, the train crosses a pole in 6 seconds. What is the value of $L$ (in metre)?
(1) 270
(2) 225
(3) 220
(4) 480
(5) 240
(IBPS RRBs Officer CWE (Pre.))
Show Answer
Correct Answer: 24. (4)
Solution: 24. (4) Let usual speed of train be $x$ kmph.
When a train crosses a platform, the distance covered
$=$ Length of train and platform = $(\mathrm{L}+240)$ metre
$\therefore \frac{60 x}{100}=\frac{\mathrm{L}+240}{15}$
$\Rightarrow \frac{3 x}{5}=\frac{\mathrm{L}+240}{15}$
Again,
$x=\frac{L}{6}$ $\quad$ ……..(ii)
$\therefore \frac{3}{5} \times \frac{\mathrm{L}}{6}=\frac{\mathrm{L}+240}{15}$
[From equation (ii)]
$\Rightarrow \frac{\mathrm{L}}{10}=\frac{\mathrm{L}+240}{15}$
$\Rightarrow \frac{\mathrm{L}}{2}=\frac{\mathrm{L}+240}{3}$
$\Rightarrow 3 \mathrm{L}=2 \mathrm{L}+480$
$\Rightarrow \mathrm{L}=480$ metre
BETA
