Question

I won 5 tickets to the Red Sox . I have 9 friends but I can only bring 4 of them. In how many ways can I form team?

Answer 1

Break the 5 tickets in half :)

Answer 2

Out of 5 tickets you have to use 1 ticket for your own and remaining 4 for other friends.

So basically you have to find how many ways you can pick 4 friends out of total 9 friends.

This can done using combination formula

`C(n,r)=(n!)/(r!*(n-r)!)`

That formula means selecting r people from n people.

We are choosing 4 out of 9 so r=4, n=9

now plug those values into above formula

`C(9,4)=(9)/(4!*(9-4)!)`

`C(9,4)=(9!)/(4!*(5)!)`

`C(9,4)=(362880)/(24*120)`

`C(9,4)=126`

So there are 126 ways to form arequired team.