A certain company is forming a committee of n people to be chosen from n married couples, where n is a two-digit even number.
Select for
No married couples the number of different committees that can be formed if no two people who are married to each other are allowed to serve on the committee, and select for
Only married couples the number of different committees that can be formed if the committee must consist only of married couples. Make only two selections, one in each column.
Total People = 2n; n married couples; n = 10 + 2x; (Two-digit Even No.)
n = 10 least 2 digit even no.; 2n = 20;
1. For the First member there are 2n candidate, then for second there can be 2n - 2 ( the first one and its spouse), like that for third 2n - 4 and for fourth 2n - 6 and so on.
And also their order doesn't matter, so the equation would be : (2n * (2n-2) * (2n-4) * (2n-6) * (2n-8) ....)/n!
20 * 18 * 16 * ....... * 2 / 10 * 9 * 8 .... = 2^10 * 10! / 10! = 2^10; = 2^n
2. For the first 2n, then the second can only be 1, then the third 2n-2, forth 1, and so on
And also their order doesn't matter, so the equation would be : (2n * 1 * (2n-2) * 1 * (2n-4) * 1 ....)/n!
20 * 18 * 16 * ......... * 12 / 10! = 2 ^ 5 * 10 * 9 * 8 ... * 6 / 10! = 2^5 / 5! = 2^(n/2) / (n/2)!