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## 3rd grade

### Course: 3rd grade > Unit 1

Lesson 6: Commutative property of multiplication# Commutative property of multiplication

CCSS.Math:

Sal explores what happens when we multiply numbers in different orders, for example 3x5 and 5x3.

## Want to join the conversation?

- Are there any other operations besides multiplication that are commutative?(46 votes)
- Addition is commutative, but subtraction and division are
**not**.(12 votes)

- why cats plus I have a cat that looks like that(10 votes)
- Cats are the meaning of life, the universe and everything in between. Without cats, the universe would not exist. According to The Cat Theory by Albert Einstein cats are supposed to be acknowledged at least 24 times a day. Thats why the mean cats were present in the video.(32 votes)

- Hi can I have 10 vote me want badge(24 votes)
- If you can tell me how I will(2 votes)

- I feel sorry for anyone who has that many angry math cats.(19 votes)
- yeah I do to.(5 votes)

- would it work the same way for three numbers that are being multiplied?(12 votes)
- Yes, it will work with three or more numbers. As long as it is all multiplication or addition(11 votes)

- Hi can I have vote pls me want badge(13 votes)
- yes you can dude(9 votes)

- Its funny you use angry cats for the equation.(10 votes)
- im a cat and i can say i do everything myself(11 votes)

- how do we repersent the communitive property of multipication(9 votes)
- The commutative (moving) property of multiplication can most simply be changing places, so 3*2=2*3. We can also use it to our advantage such as 4*4*5, 16*5 is slightly harder to do than 4*5*4 = 20*4=80. 3*6*7, 18*7 is a lot harder than 3*7*6=21*6 which can be done as 20*6+1*6.

we can represent it as a*b=b*a or a*b*c = (a*c)*b.(6 votes)

- why is this called commutative property?(8 votes)
- Don’t know. I also don’t care.(2 votes)

- Is 5x8 the same thing as 8x5(6 votes)

## Video transcript

- [Instructor] In this
video we're going to talk about one of the most important ideas in mathematics and that's
whether order matters when you multiply two numbers. So for example, is three times four the same thing as four times three? Are these two things equal to each other? And regardless of whether
these two are equal to each other, is it always the case that if I have some number times some other number, if I swap
the order am I going to get an equivalent number? Well, pause this video and see
if you can work through that. Try to think about that a little bit before we think through it together. Well, let's think through
this particular example. And we're going to do so with
the help of some angry cats. So we clearly see some angry cats here. Meow. Yes, they are angry. We could view this as
three groups of four. So this is one group right over here of angry cats, four angry cats. This is two groups of four angry cats. And this is three groups
of four angry cats if we view the first number here as groups of the second number. But we could also view it
as four groups of three. How would we do that? Well, we could have one
group of three angry cats. We can have two groups
of three angry cats. We can have three groups
of three angry cats. And we could of course have
four groups of three angry cats. So based on that, if you think of it, the first number as groups
of the second number, well, it seems like the
order doesn't matter. Another way you could think about it is here you have four
rows of three angry cats. You have one, two, three, four rows of one, two, three angry cats. And so to figure out how many total cats you have, you multiply four times three. But you could view this
same group of angry cats but just view it with a
slightly different perspective. So here we have our angry cats. And then let me rotate our angry cats, probably risking making
them a little bit angrier. Let me move them back in. And now, we could view this as three rows, one, two, three, of four cats in each row. So let me put all of these upright. So we have one, two,
three rows of one, two, three, four cats. Don't wanna look at those 'cause it might make us a little bit confused. And we're dealing with the
exact same number of cats. And so I'm only dealing
with three and four here but what you will see
is order doesn't matter when you are multiplying two numbers. And we could also see
that on a number line. And we could do that
with multiple examples. I'll keep a couple of angry cats here looking at us just to keep us in check. If we wanna think about three times four we could view it as four threes. So three, six, nine, 12. Or we could view it as three fours. Four, eight, and 12. And I focused a lot on three and four but we could do it with any two numbers that we're trying to multiply together. So let's say we wanted to do that with, I don't know, let's see
whether six times four, whether it's the same
thing as four times six. Well, you could view it as six fours. Four, eight, 12, 16, 20, and then 24. Or you could view it as four sixes. One six, 12, 18, and 24. So big takeaway, order doesn't matter when you are multiplying
numbers like this. And this is sometimes referred to as the commutative property. It's a fancy word but
it's really just saying that whether you're doing six times four or four times six the commutative property of multiplication says,
"Hey, those two things "are going to be equivalent." Meow. Yes, they are angry for being rotated.