C(n, 2) = 10. Then n = $x$.
Answer (integer)
5
Solution
C(n,2) = n(n-1)/2 = 10 → n(n-1) = 20 → n²-n-20=0 → (n-5)(n+4)=0 → n=5.
About this question
Subject: Mathematics · Chapter: Permutations and Combinations · Topic: Combinations
This question is part of PrepWiser's free JEE Main question bank. 16 more solved questions on Permutations and Combinations are available — start with the harder ones if your accuracy is >70%.