Permutation Formula

The formula for permutation is used to calculate the number of ways in which an object can be arranged without considering the order. To remember, when things or symbols are arranged in different ways and their order matters, it is known as permutation. There are two types of permutations,

Permutation with repetition: In this method, we are using it if we are being asked to make different choices each time and with different objects.

Permutation without Repetition: This comes into place when the question asks us to subtract 1 from the previous term for every occurrence.

formulas for repetition and non-repetition permutation 

Examples Using Permutation Formula

Q1: Find the number of permutations for n = 9, r = 2

Solution:

n = 9

and r = 2.

Permutation = nPr = n!/ (n−r)!

nPr = 9! /(9-2)!

= 9! /7!

= 72

Therefore, 

number of permutations = 72

Q2: Find the number of permutations you can make by rearranging letters of the word "BANANA" at a time.

Solution:

Word: BANANA

Number of letters in "BANANA" = 6

Number of "A"s in the word "BANANA" = 3

Number of "N"s in the word "BANANA" = 2

Therefore, permutation = (6!)/(3!2!)

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