Question

I run a book club with $n$ people, not including myself. every day, for $365$ days, i invite three members in the club to review a book. what is the smallest positive integer $n$ so that i can avoid ever having the exact same group of three members over all $365$ days?

Answer 1

The smallest positive integer n so that you can avoid ever having the exact same group of three members over all 365 days is; 11

How to solve probability combination?

if we have n people and we want to do groups of 5, the total number of different combinations is:

ⁿC₅ = n!/((n - 5)!5!)

By using the Brute force method, we have;

If n = 5,

c = 5,

Thus;

C₅ = 5

If n = 6,

c = 6,

Thus;

C₅ = 6

If n = 7,

c = 7,

Thus

C₅ = 21

If n = 8,

c = 8,

Then;

C₅ = 56

Now, If n = 9,

C = 9!/((9 - 5)!5!)

C = 126

We want to find the smallest n such that c > 365. Thus, C = 126 is too small.

Let's try n = 11;

C = 11!/(6! * 5!) =  462

This is greater than 365 and so we need at least 11 members in the club.

Read more about Probability combination at; brainly.com/question/16830773