 # 8 Combinations of 2

## Enter your n and r values below:

<-- Enter (n)
<-- Enter (r)

Evaluate the combination:
8C2

## Combination Definition:

A unique order or arrangement

## Combination Formula:

 nCr  = n! r!(n - r)!

where n is the number of items
r is the unique arrangements.

## Plug in n = 8 and r = 2

 8C2  2 8! 2!(8 - 2)!

## Factorial Formula:

n! = n * (n - 1) * (n - 2) * .... * 2 * 1

## Calculate the numerator n!:

n! = 8!
8! = 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1
8! = 40,320

## Calculate (n - r)!:

(n - r)! = (8 - 2)!
(8 - 2)! = 6!
6! = 6 x 5 x 4 x 3 x 2 x 1
6! = 720

r! = 2!
2! = 2 x 1
2! = 2

## Calculate 8C2

 8C2  = 40,320 2 x 720

 8C2  = 40,320 1,440  ## Excel or Google Sheets formula:

=COMBIN(8,2)

8C2 = 28

### How does the Permutations and Combinations Calculator work?

Free Permutations and Combinations Calculator - Calculates the following:
Number of permutation(s) of n items arranged in r ways = nPr
Number of combination(s) of n items arranged in r unique ways = nCr including subsets of sets
This calculator has 2 inputs.

### What 2 formulas are used for the Permutations and Combinations Calculator?

nPr=n!/r!
nCr=n!/r!(n-r)!

For more math formulas, check out our Formula Dossier

### What 4 concepts are covered in the Permutations and Combinations Calculator?

combination
a mathematical technique that determines the number of possible arrangements in a collection of items where the order of the selection does not matter
nPr = n!/r!(n - r)!
factorial
The product of an integer and all the integers below it
permutation
a way in which a set or number of things can be ordered or arranged.
nPr = n!/(n - r)!
permutations and combinations