Answer:
12C4 = 495
9P4 = 3024
Explanation:
The formula for combinations, nCr, is n!/(r!(n-r)!)
In the case of 12C4, n = 12 and r = 4:
12!/(4!(12-4)!)
(12*11*10*9*8*7*6*5*4*3*2*1)/(4*3*2*1*8*7*6*5*4*3*2*1) Cancel out like terms
(12*11*10*9)/(4*3*2*1)
11880/24
495
The formula for permutations, nPr, is n!/(n-r)!
In the case of 9P4, n = 9 and r = 4:
9!/(9-4)!
(9*8*7*6*5*4*3*2*1)/(5*4*3*2*1) We can cancel out like terms
9*8*7*6
3024