Mathematics
OpenStudy (anonymous):

For a segment of a radio show a DJ can play 9 records. If there are 12 records to select from, in how many ways can the program for this segment be arranged.

Parth (parthkohli):

See, we choose 9 from 12, so it'd be 12 choose 9 aka 12c9.

Parth (parthkohli):

Do you know what combinations are?

jimthompson5910 (jim_thompson5910):

This is similar to the last problem There are 12 choices for the first slot There are 11 choices for the second slot etc etc until you get to 3 choices for the 9th slot

Parth (parthkohli):

Basically, nCr is: $$\Large \color{MidnightBlue}{\Rightarrow {n! \over (n - r)! r!} }$$

OpenStudy (anonymous):

yes its sure been a while since i dont problems like this. thanks for the replys.

OpenStudy (anonymous):

what do i multipy thats whats throwing me off

OpenStudy (anonymous):

$\large \binom{12} 9 = \binom{12} 3= 220$