1)

A train consists of 12 bogies, each boggy 15 m long. The train crosses the telegraph post in 18 seconds. Due to some problems, two bogies were detached. The train now crosses the telegraph post in

A) 18 sec

B) 12 sec

C) 15 sec

D) 20 sec

E) 25 sec

Option C

### Explanation:

Speed of train = $\frac{length\quad of\quad train }{time}$

$=\frac{15\times 12 }{18}$

= 10 m/sec

When 2 bogies are detached, length of train $=180-30$ $=150$ m

Time taken to cross the telegraph post $=\frac{150}{10}$ = 15 sec