SOLUTION: I run a book club with $n$ people, not including myself. Every day, for $100$ days, I invite $14$ members in the club to review a book. What is the smallest positive integer $n$

Algebra ->  Percentage-and-ratio-word-problems -> SOLUTION: I run a book club with $n$ people, not including myself. Every day, for $100$ days, I invite $14$ members in the club to review a book. What is the smallest positive integer $n$       Log On


   



Question 1204712: I run a book club with $n$ people, not including myself. Every day, for $100$ days, I invite $14$ 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 $14$ members over all $100$ days?
Answer by ikleyn(52794) About Me  (Show Source):
You can put this solution on YOUR website!
.
I run a book club with n people, not including myself. Every day, for 100 days, I invite 14 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 14 members over all 100 days?
~~~~~~~~~~~~~~~~~~~~~~


        In my solution, I will assume that the person "I" does not participate in any group of 14 persons.

        The problem is silent about it, so I can make such assumption.


The number of all possible different groups of 14 members is  C%5Bn%5D%5E14.


The problem asks you to find the minimal n such that

    C%5Bn-1%5D%5E14 <= 100, but C%5Bn%5D%5E14 > 100.


Obviously, n should be not less than 14.


The table below represnts several values of n >= 14 and relevant values of C%5Bn%5D%5E14

     n          C%5Bn%5D%5E14
 -----------------------------
    14		  1
    15		 15
    16		120


From the table, you may see that the minimal n is 16.


ANSWER to the problem's question is this: the smallest positive integer  number n satisfying the problem's requirement is 16.

Solved.