in Quantitative Aptitude edited by
297 views
0 votes
0 votes

Directions for the below question:

Let $S$ be the set of all pairs $(i, j)$ where $ 1 \leq i \leq j < n$ and $n \geq 4$. Any two distinct number of $S$ are called ‘friends’ if they have one constituent of the pairs in common and ‘enemies’ otherwise. For example, if $n=4$, then $S=\{ (1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4) \}$. Here, $(1, 2)$ and $(1, 3)$ are friends, $(1, 2), (2, 3)$ are also friends, but $(1, 4)$ and $(2, 3)$ are enemies.

For general $n$, consider any two members of $S$ that are friends. How many other members of $S$ will be common friends of both these members?

  1. $\frac{1}{2} (n^2 – 5n +8)$
  2. $2n-6$
  3. $\frac{1}{2} n(n – 3)$
  4. $n-2$
  5. $\frac{1}{2} (n^2 – 7n + 16)$
in Quantitative Aptitude edited by
13.4k points
297 views

Please log in or register to answer this question.

Related questions

Quick search syntax
tags tag:apple
author user:martin
title title:apple
content content:apple
exclude -tag:apple
force match +apple
views views:100
score score:10
answers answers:2
is accepted isaccepted:true
is closed isclosed:true