Say you have 12 books, but room to display only 7. I will open this to everyone - how many differnt arrangements are there if the order of the books matters (permutation) and how many if order is of no consequence (combination)?
2 answers
lajnklh
If the order does matter than the number of permutations is 12*11*10*9*8*7*6= P(12,7) = 3991680
if the order does not matter (combinations)
it would be 12!/(7!5!) = C(12,7) = 792
both P(n,r) and C(n,r) can be found on a standard scientific calculator
usually they are labeled nPr and nCr
to do C(12,7)
enter
12
2nd F
nCr
7
=
you should get 792
if the order does not matter (combinations)
it would be 12!/(7!5!) = C(12,7) = 792
both P(n,r) and C(n,r) can be found on a standard scientific calculator
usually they are labeled nPr and nCr
to do C(12,7)
enter
12
2nd F
nCr
7
=
you should get 792
1 answer