Sal uses pictures and practice problems to see commutativity and associativity in multiplication. Created by Sal Khan.
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- What is PEMDAS?(120 votes)
Multiplication, Division (left to right)
Addition, Subtraction (left to right)(130 votes)
- what is products(13 votes)
- thank you but how is this gonna be used in my day to day life?(9 votes)
- super markets....bankers.....paying for stuff...putting stuff in your credit card to get food........buying a house.....counting for money to live :)(4 votes)
- what property is 4(x+3)=(x+3)4(7 votes)
- [Solved]At1:37do you have to put the second numbers in brackets?(6 votes)
- No, the brackets just tell you what order to operations in. With multiplication, you can do it in any order
(2x3) x4 and (3x4)x2 are going to mean the same thing.(8 votes)
- If I had an equation like this (6+3)x9 could I switch the 9 to the front of the equation like this 9x(6+3)(5 votes)
- what is exponents(5 votes)
- Good question for 3rd grade!
The exponent (or power) is a raised number that tells us how many times to multiply the base (bottom number) by itself.
Example: if the base is 2 and the exponent is 3, we get 2 * 2 * 2 = 8.
So 2 to the 3rd power is 8.
This is also written as 2^3 = 8.
Note that 3^2 would give a different answer: 3 * 3 = 9.
So the order of the base and the exponent is important.
Later in math, you will learn how to do calculations with zero, negative, and fractional exponents.
Have a blessed, wonderful day!(7 votes)
- what is pemdas?(5 votes)
- Pemdas is a abbrevation that is very useful in telling you the order in which you solve in a multi-step problem. An easy way to remember it is Please Excuse My Dear Aunt Sally As I'm sure it explained in the video, it stands for:
Just a quick disclaimer- When you are on the multiplication/division step in solving an equation, whatever comes first is the thing that is solved. This means, when you are reading it from left to right, if division is before multiplication, do the division first. This is the same for addition/subtraction.(6 votes)
- The video made it sound as if the commutative and associative property are the same things...the commutative is when you can move around the numbers (any order) and the associative is when you can move the parentheses? Doing either, you would still get the same answer? Correct?(6 votes)
- How did he know 8 divided by 3 was a fraction of 8 over 3?(3 votes)
So if you look at each of these 4 by 6 grids, it's pretty clear that there's 24 of these green circle things in each of them. But what I want to show you is that you can get 24 as the product of three numbers in multiple different ways. And it actually doesn't matter which products you take first or what order you actually do them in. So let's think about this first. So the way that I've colored it in, I have these three groups of 4. If you look at the blue highlighting, this is one group of 4, two groups of 4, three groups of 4. Actually, let me make it a little bit clearer. One group of 4, two groups of 4, and three groups of 4. So these three columns you could view as 3 times 4. Now, we have another 3 times 4 right over here. This is also 3 times 4. We have one group of 4, two groups of 4, and three groups of 4. So you could view these combined as 2 times 3 times 4. We have one 3 times 4. And then we have another 3 times 4. So the whole thing we could view as-- let me give myself some more space-- as 2 times-- let me do that in blue-- 2 times 3 times 4. That's the total number of balls here. And you could see it based on how it was colored. And of course, if you did 3 times 4 first, you get 12. And then you multiply that times 2, you get 24, which is the total number of these green circle things. And I encourage you now to look at these other two. Pause the video and think about what these would be the product of, first looking at the blue grouping, then looking at the purple grouping in the same way that we did right over here, and verify that the product still equals 24. Well, I assume that you've paused the video. So you see here in this first, I guess you could call it a zone, we have two groups of 4. So this is 2 times 4 right over here. We have one group of 4, another group of 4. That's 2 times 4. We have one group of 4, another group of 4. So this is also 2 times 4 if we look in this purple zone. One group of 4, another group of 4. So this is also 2 times 4. So we have three 2 times 4's. So if we look at each of these, or all together, this is 3 times 2 times 4, so 3 times 2 times 4. Notice I did a different order. And here I did 3 times 4 first. Here I'm doing 2 times 4 first. But just like before, 2 times 4 is 8. 8 times 3 is still equal to 24, as it needs to, because we have exactly 24 of these green circle things. Once again, pause the video and try to do the same here. Look at the groupings in blue, then look at the groupings in purple, and try to express these 24 as some kind of product of 2, 3, and 4. Well, you see first we have these groupings of 3. So we have one grouping of 3 in this purple zone, two groupings of 3 in this purple zone. So you could do that as 2 times 3. And we have one 3 and another 3. So in this purple zone, this is another 2 times 3. We have another 2 times 3. Whoops. I wrote 2 times 2. 2 times 3. We have another 2 times 3. And then finally, we have a fourth 2 times 3. So how many 2 times 3's do we have here? Well, we have one, two, three, four 2 times 3's. So this whole thing could be written as 4 times 2 times 3. Now, what's this going to be equal to? Well, it needs to be equal to 24. And we can verify 2 times 3 is 6 times 4 is, indeed, 24. So the whole idea of what I'm trying to show here is that the order in which you multiply does not matter. Let me make this very clear. Let me pick a different example, a completely new example. So let's say that I have 4 times 5 times 6. You can do this multiplication in multiple ways. You could do 4 times 5 first. Or you could do 4 times 5 times 6 first. And you can verify that. I encourage you to pause the video and verify that these two things are equivalent. And this is actually called the associative property. It doesn't matter how you associate these things, which of these that you do first. Also, order does not matter. And we've seen that multiple times. Whether you do this or you do 5 times 4 times 6-- notice I swapped the 5 and 4-- this doesn't matter. Or whether you do this or 6 times 5 times 4, it doesn't matter. Here I swapped the 6 and the 5 times 4. All of these are going to get the exact same value. And I encourage you to pause the video. So when we're talking about which one we do first, whether we do the 4 times 5 first or the 5 times 6, that's called the associative property. It's kind of fancy word for a reasonably simple thing. And when we're saying that order doesn't matter, when it doesn't matter whether we do 4 times 5 or 5 times 4, that's called the commutative property. And once again, fancy word for a very simple thing. It's just saying it doesn't matter what order I do it in.