Answer: 12
Step-by-step explanation:
If we have n people and we want to do groups of 4, the total number of different combinations is:
[tex]c = \frac{n!}{(n - 4)!4!}[/tex]
and we want find the smallest n such c > 365.
let's do it by brute force:
if n = 5, we have:
[tex]c = \frac{5!}{1!*4!} = 5[/tex]
if n = 6
[tex]c = \frac{6!}{2!*4!} = \frac{6*5}{2} = 15[/tex]
if n = 7
[tex]c = \frac{71}{3!*4!} = \frac{7*6*5}{3*2} = 35[/tex]
if n = 8
[tex]c = \frac{8!}{(4!*4!} = \frac{8*7*6*5}{4*3*2} = 70[/tex]
if n = 9
[tex]c = \frac{9!}{5!*4!} = \frac{9*8*7*6*5}{5*4*3*2} = 126[/tex]
if n = 10
[tex]c = \frac{10!}{6!*4!} = \frac{10*9*8*7}{4*3*2} = 210[/tex]
So you can see the patern here.
So we have the previous number multiplied by n and divided by n - 4
if n = 11
C = 210*11/(11- 4) = 330
if n = 12
C = 330*12/(12 - 4) = 495
Then the minimum number of members such we have more than 365 combinations is 12 members
