Discussion Forum



Each of the questions given below consists of two statements numbered I and II given below it. Please read the questions carefully and decide whether the data provided in the statement(s) is / are sufficient to answer the given question.

1)

A train crosses a signal post in $x$ seconds. What is the length of the train ?

I. The train crosses a platform of 100 metres in $y$ seconds.

II. The train is running at the speed of $80$ km/hr.


A) I alone sufficient while II alone not sufficient to answer

B) II alone sufficient while I alone not sufficient to answer

C) Either I or II alone sufficient to answer

D) Both I and II are not sufficient to answer

E) Both I and II are necessary to answer

Answer:

Option C

Explanation:

Let the length of the train be $a$ metres.

Time taken to cross a signal post = Length of the train $\div$ Speed of the train $\Rightarrow x=\frac{l}{Speed}$. ----(1)

Time taken to cross the platform $=\frac{(l+100)}{Speed}$ $\Rightarrow y=\frac{l+100}{Speed}$ ----(2)

Thus, from (1) and (2), we can find $l$.

Also II gives, speed $=\left(80\times\frac{5}{18}\right)$ m/s $=\frac{200}{9}$ m/s.

Thus, the data in I or II are sufficient to answer the question.

$\therefore$ The correct answer is (C).