Perms and combs is all about counting.
You count the number of ways certain things can happen, different ways you can do them, and the number of different possible results from what you do.
For example, if there are three different T-shirts hanging within your wardrobe, there are three different ways of choosing a T-shirt from this wardrobe, and similarly the T-shirts could be arranged in six different ways along a line.
The thing you do is usually called a process, or an operation. In the previous example the choosing of a T-shirt is a process, and arranging the T-shirts is also a process too.
Rolling a die/dice, flipping a coin, and arranging people in a line are commonly processes used in perms and combs.
What is an outcome? An outcome of a process is a result from doing the process. For example, getting a “3” from rolling a die, or choosing the first T-shirt, are both outcomes from their respective processes.
The idea of processes and outcomes are also used in probability, as you will see later chapters.
There are two main and easy rules to count. These will help you find and understand perms and combs.
To easy? Carry on to the next page, and we’ll see…