Commutative Law of Addition

Use the commutative law of
addition-- let me underline

that-- the commutative law
of addition to write the

expression 5 plus 8 plus 5
in a different way and

then find the sum.

Now, this commutative law of
addition sounds like a very

fancy thing, but all it means
is if you're just adding a

bunch of numbers, it doesn't
matter what order you add the

numbers in.

So we could add it as
5 plus 8 plus 5.

We could order it as
5 plus 5 plus 8.

We could order it
8 plus 5 plus 5.

These are all going to add up
to the same things, and it

makes sense.

If I have 5 of something and
then I add 8 more and then I

add 5 more, I'm going to get
the same thing as if I had

took 5 of something, then added
the 5, then added the 8.

You could try all
of these out.

You'll get the same thing.

Now, they say in a different
way, and then find the sum.

The easiest one to find the sum
of-- actually, let's do

all of them.

But the easiest one, just
because a lot of people

immediately know that 5 plus 5
is 10, is to maybe start with

the 5 plus 5.

So if you have 5 plus
5, that's 10, plus

8 is equal to 18.

Now, let's verify that these two
are the same exact thing.

Up here, 5 plus 8 is 13.

13 plus 5 is also 18.

That is also 18.

If we go down here,
8 plus 5 is 13.

13 plus 5 is also equal to 18.

So no matter how you do it and
no matter what order you do it

in-- and that's the commutative
law of addition.

It sounds very fancy, but it
just means that order doesn't

matter if you're adding
a bunch of things.