- Intro to Combinations and Permutations
- Permutations with Repetition
- Permutations without Repetition
- Permutations Formula
- Android Lock Screen
- Tigers and Bears - Oh My
Combination without Repetition
- Combination Formula
- Combining Combinations
The String of Beads
- Combinations with Repetition I
- Combinations with Repetition II
To calculate the number of possible combinations of r elements from n elements, you can do the following:
- Calculate (n Permute r)
- Divide nPr by r!, the number of permutations of r itself. This is because there will be r! permutations for each combination.
The Combination formula can be expressed as one formula. Recall the permutation formula:
You can then just divide by r! to get the Combination formula:
r! * (n-r)!
This formula can be shortened to:
(n choose r) on a calculating device, though again there may be cases where the formula does not apply.
In the powerball lottery, 5 balls are chosen from 59 different white balls and 1 ball is chosen from 35 different red balls. The order they are chosen in does not matter. How many outcomes are possible?
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