repeated permutation: Three number, how many permutation 103.
Another Three position, For each position, you can select 10 options
and fill it. If three position, For each position, you can selet 2 options
and fill it. You get powerset problem 23 {a,b, c} all the subset.
unrepeated permutation: n! = factorialfunction
unrepeated combination:
repeated combination:
detail can been seen here: https://www.mathsisfun.com/combinatorics/combinations-permutations.html
