remember last weeks activity? first you estimated area - maybe counted squares?? this square has 35...
DESCRIPTION
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 unitsTRANSCRIPT
Remember last weeks activity? First you estimated area - maybe counted
squares??
This square has 35 whole squares and 10 partsquares 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 parallelogramLength = BaseWidth = Heightl 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 heightA = b x hA = 8 x 5A = 40 u2
Area = base x heightA = b x hA = 8 x 5A = 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 HeightA = b x hA = A =
How about this one?