Answer:
nCr = n! / (r!)(n-r!).
Step-by-step explanation:
That would be nCr = n! / (r!)(n-r!).
A quick way of working these out is as follows:
Take 7C4:
this is 7*6*5*4/4*3*2*1 Cancelling out the 4 and 3*2:
= 7*5
= 35.
15C12 = 15C(15-12)
= 15C3
= 15*14*13 / 3*2*1
= 5*7*13
= 455.
