- #1
musicgold
- 304
- 19
Hi,
I am not sure which formula will allow me to get the following results.
If I have to pick two letters from A, B, C, D, then there are 6 possible combinations:
AB
AC
AD
BC
BD
CD.
Now assume that letter D has turned into another A, i.e. A2. Now my combinations have changed to
A1B
A1C
A1A2
BC
BA2
CA2
So I eliminate BA2, and CA2 and I have 4 unique combinations.
I know that in the case of permutations with repetitions, we divide the nPr formula by the factorials of the frequency of the letters, but I am not sure how it is done with combinations. What formula can use for combinations?
Thanks.
I am not sure which formula will allow me to get the following results.
If I have to pick two letters from A, B, C, D, then there are 6 possible combinations:
AB
AC
AD
BC
BD
CD.
Now assume that letter D has turned into another A, i.e. A2. Now my combinations have changed to
A1B
A1C
A1A2
BC
BA2
CA2
So I eliminate BA2, and CA2 and I have 4 unique combinations.
I know that in the case of permutations with repetitions, we divide the nPr formula by the factorials of the frequency of the letters, but I am not sure how it is done with combinations. What formula can use for combinations?
Thanks.