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# Permutations

Suppose you want to know how many combinations of looks you can do with the set of clothes that you have, what mathematical solution do you think you can use so you don’t have to mentally count all of the possible outcomes? How about, if you want to know how many kinds of arrangement you can do with the chairs in the classroom? In order to solve these problems you will need to know about permutations and combinations.

This chapter will have nine parts which will help us understand the basic concept of permutation and combination. In the first part of chapter, we will discuss about the fundamental counting principle. This principle states that if two separate events have m and m possible outcomes respectively, then the combined possible outcome for the combined events would be equivalent to m x n.

In the second part of this chapter will review how to write and solve a factorial notation. For example, if you are asked to solve four factorial or 4!, then you know that you need to solve for 1 x 2 x 3 x 4. Factorial notations are used throughout our discussion in this chapter like in proceeding parts of the chapter that focuses on path counting, and the difference between permutation and combination.

For the eighth this chapter, we will look into the application of all the concepts about permutations and combinations with that of the Pascal's triangle. If you want to know the answer for the question “what is a Pascal’s triangle?” you can check on it on various resources online.

Finally, in the last part of the chapter, we will look into the Binomial theorem. This theorem is used to find any power of a certain binomial without the need to multiply a long list of terms.

### Permutations

Imagine, you want to withdraw cash from the ATM machine, but you forget the password of your account. The only thing you remember is that the password consists of the number 1, 2, 3, and 4. You are now trying to figure out the number of ways to arrange the numbers, and that’s permutations. Unlike combinations, order matters in permutations!