Yay!!! We continue the lessons of Counting.

Today we will do basic counting of certain objects.

Example 1:

How many ways can you arrange the letters in the word: WORD.

Lets see how to figure this question out.

For the first letter, there are 4 possiblities, W, O, R or D.

So 4 _ _ _

Now we have 3 left over:

4 3 _ _

And it continues to 4,3,2,1, which is 24.

This is also known as factorials.

4! (!=factorial) =24

W-O-R-D

W-O-D-R

W-R-O-D

W-R-D-O

W-D-O-R

W-D-R-O

continued...

Here is a table of some factorials.

1!=1

2!=2

3!=6

4!=24

5!=120

6!=720

7!=5040

...

Now lets look at another problem.

Example 2:

Coins.

How many outcomes are there for 3 coins?

For the first coin, we either have a head or a tail. (H,T)

Using the same method as above, we have 2x2=4

These are just powers of 2.

_________________

~Dojo