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### Course: 3rd grade > Unit 10

Lesson 6: Decompose figures to find area# Decomposing shapes to find area: add

Let's find the area of an irregular 10-sided shape by breaking it into smaller rectangles. We'll learn to decompose complex shapes, calculate the area of each rectangle, and combine those areas to find the total area, making the topic engaging and enjoyable. Created by Lindsay Spears.

## Want to join the conversation?

- Is m for meters?(19 votes)
- Yes, m stands for meters, like how ft stands for feet.(6 votes)

- Can you learn this in every boarding school or only certain boarding schools?(4 votes)
- I do not know.Why are you asking? That is my question.Welp that's weird a question on a question?CRAZY(1 vote)

- What happened to the 6 on the bottom? The area should be 48 square meters.(3 votes)
- The
`6m`

on the bottom became`3m`

. For the reason that, if you look at the top of the shape when Sal split it up, there was a`3m`

distance at the very top, and when Sal decomposes the shape, he split the`6m`

piece into two`3m`

pieces resulting in the removal of the`6m`

into two`3m`

's instead!*Hope this helps!*(2 votes)

- What if there is a triangle mixed in with the shape... how do I solve for that?(2 votes)
- That's gonna be finding an area of a triangle, that will come in higher grades.(2 votes)

- Why haven't they explain what "square meters" means?(0 votes)
- Square meters are a form of measurement, like square feet or squares inches.(5 votes)

- you can learn so much stuff on khan academy(1 vote)
- I think that the things that are taught on khan academy in 3rd grade should be taught in 2nd grade. (I already knew the stuff on 3rd grade in khan academy when I was in 2nd grade.)(3 votes)

- i like this vid(2 votes)
- Who am i I am who(1 vote)
- I dont get why theres a six at the bottom, your not even using it, what is the purpose of having a number that your not even using and how do you know not to use that number in the eqaution?(1 vote)
- Sometimes they put extra, useless numbers in math problems just to make sure you're really paying attention and truly know how to do the problem. It can be frustrating, I know. But with practice you'll grow more careful and improve your math skills.(0 votes)

- just so you know when you split the green part into sixths,

the fractions were not equal.(0 votes)

## Video transcript

- [Voiceover] What is
the area of the figure? So down here we have this one, two, three, four, five, six, seven,
eight, nine, 10-sided figure, and we want to know its area, how many square meters
does this figure cover? And we have some measurements, that seems helpful, but what's not too helpful to me is I don't know the special trick to find the area of a 10-sided figure so I've got to think about what I do know and what I do know is the way to find area of a rectangle. So what I can do, because I can see, if I can find any rectangles in here. Here's one rectangle, right there. So I can find the area of that part. Then let's see if I can find any more. Here's another rectangle. So I can find the area of that part. We could call that one
a rectangle or a square. And then that leaves
us with this last part, which is again, a rectangle. So what we did is, we broke this up or decomposed it into three rectangles and now if I find out how much space this purple one covers, and the blue one and the green one, if I combine those, that
would tell me the area of the entire figure, how much space the entire figure covers. So let's start with this one right here. This one is three meters long, so we can kind of divide
that by three meters, into three equal meters, and then we've got a width
of two meters down here so we can split that in half. So if we draw those lines out, we can see this top row is
going to cover one square meter, two square meters, three square meters, and then there's two rows of that, so there's two rows of three square meters for a total of six square meters. This rectangle covers six square meters, so this part of the entire figure covers six square meters. The next one, our measurements
are three and a three, so it will have three rows
of three square meters or nine square meters, and then finally this purple one has three meters and nine, so we can say it will
have three rows of nine or nine rows of three square meters which is 27 square meters. So the area of this purple section, it covers completely 27 square meters. The green covers nine square meters, and the blue covered six square meters. So, if we combine all those areas, all those square meters it covers, that will tell us the
area of the entire figure. So we have six square meters, plus nine square meters, plus 27, and we can solve that,
six plus nine is 15, 15 plus 27, let's see, five ones and seven ones is 12 ones. We'll just find some space up there. And one 10 and two 10's or a 10 and a 20 is 30. And 30 plus 12 is 42. So the area of the entire figure is 42 square meters.