✔ 最佳答案
你0的notes符號有些亂﹐我係到直接寫番個正確既answer
Permutations with Repetition:
The number of different permutations of n objects, where there are n1 indistinguishable objects of style 1, n2 indistinguishable objects of style 2, ..., and nk indistinguishable objects of style k, is ;
圖片參考:
http://www.regentsprep.org/Regents/math/ALGEBRA/APR2/LpermR8.gif
Example:
1. How many different 5-letter words can be formed from the word APPLE ?
answer
5!/2!=120/2=60
2! because the letter P repeats twice.
2. How many different six-digit numerals can be written using all of the following six digits:
4,4,5,5,5,7
answer
6!/2!3!=720/12=60
Two four and three fives repeat, so divide by 2! and 3!