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Current time:0:00Total duration:3:36

Decomposing shapes to find area: add

CCSS.Math: ,

Video transcript

what is the area of the figure so down here we have this one two three four five six seven eight nine ten 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 ten 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 is I can see if I can find any rectangles in here here's one rectangle right there so I could find the area of that part then let's see if I can find anymore 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 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 kind of divide that by three meters into three equal meters and then we got a width of two meters down here so just put 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 or 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 meter 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 of covers that will tell us the area of the entire figure so we have 6 square meters plus 9 square meters plus 27 and we can solve that 6 plus 9 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 110 and two tens 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