Grade 12 Data Management – Permutations
- If one operation can be performed in K1 ways, and for each operation that can be performed K2 ways, and for each operation that can be performed K3 ways..
- All of these ways can be performed K1 x K2 x K3.. ways
- If one mutually exclusive action can occur in K1 ways and a second can occur in K2 ways, then there are K1 + K2.. ways in which these actions can occur.
- If a set of operations can be used to determine a result, then it’s called Direct Method
- However, if it is difficult to determine directly, an indirect method may be used by subtracting certain possibilities so they are eliminated
- For the following: r < n
- n! = n(n-1)(n-2)(n-3)(n-4)… (n-r+1)(n-r)!, n belongs to natural numbers
- n!/(n-r)! = n(n-1)(n-2)(n-3)(n-4)… (n-r+1)(n-r)!/(n-r)!
- ie. 6! = 6*5*4*3*2*1
Permutations with some elements alike
- In general, the number of different arrangements of n objects K1 alike of one kind and k2 alike of another kind is:
n! / (k1!)(k2!)
- ie. in the word “COOL”, the permutations are as follows:
4! / (2!) = 12