Subject: General Aptitude · Chapter: Problems on Trains · Exam: · Marks: · Difficulty:
What is the length of a running train? I. The train crosses a man in 9 seconds. II. The train crosses a 240 metre long platform in 24 seconds.
Answer
SELF-PRACTICE — the source book printed no answer.
Nothing is invented here, so this question has no answer on record.
Explanation
Time taken by train to cross a man $=\frac{\text { Length of train }}{\text { Speed of train }} \Rightarrow \text { Speed }=\frac{l}{9}$ Time taken by train to cross a platform $=\frac{(\text { Length of train }+ \text { Length of platform) }}{\text { Speed of the train }} \Rightarrow \text { Speed }=\frac{l+240}{24}$ From (i) and (ii), we get $\frac{l}{9}=\frac{l+240}{24}$. Thus, $l$ can be obtained. So both I and II are necessary to get the answer. ∴ The correct answer is (e).
Explanation as extracted from the printed page; notation may be imperfect.