Question

Ross has sixteen photos of his friends. In how many ways can he choose twelve of the photos to add to his photo album? A. ( 16

12
) B. 2 16
C. 12!
16!
D. 4 ! E. 4!
16!

Answer 1

Answer:
`\displaystyle (16!)/(12!4!)`

Reason:

Recall that the nCr combination formula is
`_nC_r = (n!)/(r!(n-r)!)`

We plug in n = 16 and r = 12 to end up with the answer above. We use the nCr combination formula since order doesn't matter. Optionally we can use a calculator to compute that factorial fraction to get a single numeric value, but I'll leave it as is to match with what the answer choices appear to be.