<em><u>~permutation~</u></em>
Permutation is a term that in mathematics refers to several different meanings in different areas.
Permutation can be permutation with repetition and permutation without repetition.
nPr=
(n−r)!
n!
<em><u>~</u></em><em><u>Permutation</u><u> </u><u>without</u><u> </u><u>repetition</u></em><em><u>~</u></em>
Permutation means to combine the default elements in all possible ways so that each group contains all the default elements.
The number of permutations of a set of n different elements is equal Pn=n×(n-1)×...×2×1=n!
<em><u>~</u><u>Permutation with repetition</u><u>~</u></em>
If between n given elements there are k1 equals of one kind, k2 equals of another kind,..., ky equals of rth kind, we speak of permutations with repetition.
<em><u>~combinations without repetition~</u></em>
In many counting problems, the order of the selected elements is not important.
Each choice of r different elements of an n-member set determines one of its subsets that has r elements, we call it a combination of r-th class without repetition of n elements.
nCr=
r!(n−r)!
n!
<em><u>~combinations with repetition~</u></em>
Repetition combinations are combinations in which elements can be repeated.
<em><u>~Variations without repetition~</u></em>
A variation of the r-th class in an n-membered set is each ordered r-torque of different elements.
(We can determine this number using the principle of consecutive counting).
<em><u>~Variations with repetition~</u></em>
If the elements in ordered r-tuples can be repeated we are talking about variations with repetition.
(We can determine this number using the principle of consecutive counting).