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## 3rd grade

### Course: 3rd grade > Unit 10

Lesson 3: Area formula intuition# Area with partial grids

Explore the concept of finding area with partial arrays. Learn how to determine the area of partial rectangles by completing the rectangle with lines, similar to a grid. Created by Sal Khan.

## Want to join the conversation?

- What is 183 plus 285? Solomon.(1 vote)
- When there are high digits, there are often good tricks.

183 is just 20 less than 203.

So we can add 203 + 285 to get 488, then subtract 20 to get 468.

Have a blessed, wonderful day!(7 votes)

- i refuse to believe these comments r from actual humans(2 votes)
- Day 1 of commenting

how is geometry dash 2.2 so close(1 vote) - guys this is easy, we learned this in like 1st grade.(1 vote)
- Why are these so long?It takes so much time that i could be doing a activity!(1 vote)
- Out of curiosity, is there any line of work where you would need to find the area of a partial grid? Where would one find partial grids?(0 votes)

## Video transcript

- [Teacher] We're told,
"The following rectangle is partially split into unit squares. What is the area of the rectangle above?" So pause this video and see
if you can figure that out. Alright, now let's do this together. So first it's good to just
know what do they mean when they say area? Well, they say it's partially
split into unit squares. When they're talking about a unit square they're talking about a square like this. And when we're talking about area, we're talking about how
many of these unit squares would exactly cover this entire shape. That many unit squares would be the area of this entire rectangle. So how could we do that? Well, what we could do is we
could keep drawing these lines that have already been partially drawn, and we can then see how many
of these unit squares we have. So let's just finish
drawing these lines here. I'll try to draw it as neatly as I can. So we have that. We have that like there. And then let me complete this one, and let me complete that
one. I'm almost done. That one and then that one. And so what we have here, let's see how many rows do we have? We have 1, 2, 3, 4, 5 rows. And in each of those rows, let
me do it this way, five rows. And in each of those rows,
how many squares do we have? Let's see, we have 1, 2, 3, 4. So you could view it as,
we have five rows of four. So how many total of
these unit squares exactly cover this rectangle? Well, we could just count them. We could see that that is going to be, well it's gonna be five rows of four. So it's gonna be one row, that's four. then another four, then another
four, and then another four, and then another four. And let's see, yep, I
have five fours here. I'm adding the five
rows of four each there. And what is that going to be equal to? Well, this is going to be equal
to four, plus four is eight, plus four is 12, plus four
is 16, plus four is 20. So the area of the rectangle
above is going to be 20. And it's important to say, "20 of what?" It's 20 square units. Or maybe I could say
unit squares. Either way. But I'll call it square units. And we are done.