# Combinatorics (Combinations)

by
**andresesqueda**

Last updated 7 years ago

** Discipline: **

Math ** Subject: **

Algebra I
** Grade:**

10

In conlusion we now know at least different formulas in which we could use combinations for different problems. It is most useful when we are trying to find how many things we want without order importance. Although there could be repetition sometimes, for example when selecting an ice cream flavor.

Matze H, Andres Esqueda, Rodrigo Lopez, Adrian Marin. P-4

Formulas used

Combinatorics and Probabilities

Combinations

There are two type of combinations.

Steps

1) Combination without repetition: In combinations order doesn't matter, so basically if you have a few items and grab them randomly, since they are not repeating and the order doesn't matter that would be a combination without repetition. 2)Combinations with repetition: Now in combinations with repetition, order does not matter and now there can be items repeated.

ExampleMin. 11:46

Where n is the number of things to choose from, and you choose r of them (No repetition, order doesn't matter)

Instead of the big parentheses we use notation.

Use our permutations formula to reduce it by how many ways the objects could be in order because we don't care about the order.

Without repetition

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