1. Where do Area Formulas Come From?

2. Important Terms: Base and Height
Base and height always make a right angle.

3. The Rectangle: A Basic Shape
The Basic Grid: 12 units2
A = bh

4. The Parallelogram
A = bh

5. The Triangle
A = ½ bh

6. The Trapezoid

7. Summary Area of a rectangle = bh Area of a square = s2
Area of a triangle = ½ bh
Area of a trapezoid = ½ h(base 1 + base 2)

8. Area of a Circle
A =πr2

9. Easy Way to Memorize Circle Formulas
Circumference Formula
Area Formula
C =πd
A =πr2
“Cherry pie’s delicious, apple pies are too”

10. What are the area formulas for these shapes?
The Semicircle
The Quarter-Circle