A train consists of 12 boggies, each boggy 15 metres long. The train crosses a telegraph post in 18 seconds. Due to some problem, one boggies were detached. The train now crosses a telegraph post in	Choose one:
A) 16.5 sec  B) 12 sec  C) 15 sec  D) 20 sec  E) none of these

Rationale: length of train = 12 ã — 15 = 180 m . then , speed of train = 180 â  „ 18 = 10 m / s now , length of train = 11 ã — 15 = 165 m â ˆ ´ required time = 165 â  „ 10 = 16.5 sec . answer a
Answer: A