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Lesson 6: Decompose figures to find area

# Decomposing shapes to find area: grids

Lindsay finds the area of an irregular shape by decomposing it into 2 rectangles.  Created by Lindsay Spears.

## Want to join the conversation?

• How is this important to us?
• This could be useful to many job purposes. One example is being an architect. Suppose you need to design a house for efficiency and low cost. Part of the house that you are building might be in an irregular shape style. You would have to know the area of it because it could help you put things like a bed inside. If you just randomly make a house with no blueprints or area models, you definitely would mess up. You could make a room too small or forget to place a door. There are many more ways that math can help us in our life, but this is just one of them. Hope this helped! -Johnny Unidas
• Hello I don't understand what do we do when grids are not there
(1 vote)
• Usually, if a grid is not present, some sort of measurements is on the object in the shape of distances, say `1cm` or `3cm` on a length or a width that you can use. So do not worry about that, you can and will be able to find the area.

Hope this helps!
(1 vote)
• How does it cover 2 sq cm?
• The shape does not cover `2cm²`, the total area is `24cm²` as the two shapes have the areas of `14cm` and `10cm` adding to the total area of the shape.

It does this through the following multiplication and addition sequences:

``  5cmx 2cm——————— 10cm²``

This is the area of the first one of the shapes, a total of `10cm²`

``  2cmx 7cm————————  14cm²``

This is the area of the second one of the shapes, a total of `14cm²`

Now, what we have to do is add both the numbers up to get the total area:

``  14cm²x 10cm²————————  24cm²``

So, therefore, we can make the conclusion that the area of both the shapes combined are 24cm².

Hope this helps!
(1 vote)
• How come you have to divide it?Because I no I don’t