Let n>2 be an integer. Suppose that there are

Question:

Let $n>2$ be an integer. Suppose that there are $n$ Metro stations in a city located along a circular path. Each pair of stations is connected by a straight track only. Further, each pair of nearest stations is connected by blue line, whereas all remaining pairs of stations are connected by red line. If the number of red lines is 99 times the number of blue lines, then the value of $n$ is :

  1. (1) 201

  2. (2) 200

  3. (3) 101

  4. (4) 199


Correct Option: 1

Solution:

(1) Number of two consecutive stations (Blue lines) $=n$ Number of two non-consecutive stations (Red lines)

$={ }^{n} C_{2}-n$

Now, according to the question, ${ }^{n} C_{2}-n=99 n$

$\Rightarrow \frac{n(n-1)}{2}-100 n=0 \Rightarrow n(n-1-200)=0$

$\Rightarrow n-1-200=0 \Rightarrow n=201$

 

Leave a comment

Close

Click here to get exam-ready with eSaral

For making your preparation journey smoother of JEE, NEET and Class 8 to 10, grab our app now.

Download Now