Subject: General Aptitude · Chapter: Problems on Trains · Exam: · Marks: · Difficulty:
What is the length of a running train P crossing another running train Q? I. These two trains take 18 seconds to cross each other. II. These trains are running in opposite directions. III. The length of train Q is 180 metres.
(a)I only
(b)II only
(c)III only
(d)All I, II and III are required
(e)Even with I, II and III, the answer cannot be obtained.
Answer
Answer (as printed): E
Explanation
Let the length of train P be x metres. II. These trains are running in opposite directions. III. Length of train Q is 180 m. I. Time taken by P to cross Q $=\frac{180+x}{\text{Relative speed}}$ $\Rightarrow 18=\frac{180+x}{\text{Relative speed}}$. Thus, even with I, II and III, the answer cannot be obtained. Correct answer is (e).
Explanation as extracted from the printed page; notation may be imperfect.