Objective

​To find area of parallelograms, triangles, trapezoids, and circles.

We can think of the area of a two-dimensional ("plane") object as the number of square units it contains.

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Each of the figures to the right has the same area.

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You can see that counting boxes sometimes works well and sometimes not.​

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Fortunately, there are formulas so we don't have to count boxes

Rectangle formula is pretty straightforward

In middle school you probably learned "length times width" but because the formulas of many shapes are related we want to develop some common language. So we will say the area of a rectangle is "base times height".

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​On the next slide we'll look at the relationship between area of a rectangle and area of a triangle.

​https://www.geogebra.org/m/jmgu5t2z

Let's Practice

A reminder

​Recall from Unit 6 (properties of polygons)

The trapezoid area formula has a slight twist. It is half the height times the sum of the two bases.

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Independent practice

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