Given:
Total number of friends = 9
Number of friend to invite = 4
To find:
The number of ways.
Solution:
We know that, total number of ways to select r items from n items is
[tex]^nC_r=\dfrac{n!}{r!(n-r)!}[/tex]
So, the total number of ways to select 4 people from 9 friends is
[tex]^9C_4=\dfrac{9!}{4!(9-4)!}[/tex]
[tex]^9C_4=\dfrac{9!}{4!5!}[/tex]
[tex]^9C_4=\dfrac{9\times 8\times 7\times 6\times 5!}{4\times 3\times 2\times 1\times 5!}[/tex]
[tex]^9C_4=\dfrac{9\times 8\times 7\times 6}{4\times 3\times 2\times 1}[/tex]
Therefore, the required number of ways is [tex]\dfrac{9\times 8\times 7\times 6}{4\times 3\times 2\times 1}[/tex].
Note: All options are incorrect.
