Remember last weeks activity? First you estimated area - maybe counted squares?? This square has 35 whole squares and 10 part squares that are ½ or greater = 40

Then you drew and cut and pasted: You ended up with a rectangle exactly the same size as this initial parallelogram… You calculated that the area of the rectangle was 8 x 5 = 40 square units

But we want to be able to calculate area exactly and without having to count squares. How?

First let’s get used to some new vocabulary: A rectangle is a parallelogram Length = Base Width = Height l x w is the same as b x h Notice the height (dotted line) Is perpendicular to, or at a 90° angle with the base.

So… we have a new formula Area = base x height A = b x h A = 8 x 5 A = 40 u 2 Area = base x height A = b x h A = 8 x 5 A = 40 u2

Very important to Remember!!! The base and the height must be perpendicular – at a 90° angle with each other. Notice that the lateral sides of a parallelogram are NOT perpendicular to the base. Thus, a dotted line is drawn to represent the height. Let’s look at a couple examples:

Try this one: Use our formula: Area of a parallelogram = Base x Height A = b x h A =

How about this one?