1. Finding Area of Other Polygons
Math 6
Finding Area of Other Polygons

2. Objectives:
Find the area of right triangles, other triangles, special quadrilaterals, and polygons by composing into rectangles or decomposing into triangles and other shapes.
6.G.1

3. Keys to Geometry Master the vocabulary Polygon Trapezoid rhombus
parallelogram
Complex figure
Regular polygon

4. Online Math Dictionaries

5. Review: Area of a rectangle
Multiply length times width

6. Area of a triangle
Since a triangle with the same dimensions takes up only half as much space as a rectangle, we multiply and then divide by 2.

7. We can find the area of many other shapes based on those two formulas.

8. Parallelogram A=b h

9. Key Point As with a triangle, you must multiply base times the height.
The height is not the length of the side.
The height is a line that is perpendicular to the base.

10. What measurements would you use in this example?

11. Why does it work?
Let’s compare it to the other two formulas we’ve learned…

12. What is this figure called?

13. Area of a trapezoid

15. Guided Practice

16. Guided Practice

17. Guided Practice

18. Guided Practice

19. When would you need to know the lengths of the sides?
Guided Practice
When would you need to know the lengths of the sides?

20. Guided Practice

21. Guided Practice
A sailboat has a triangular sail with a base of 18 feet and an area of 270 square feet. How tall is the sail?

22. Conclusion
Connect how to find the area of a parallelogram, rhombus and trapezoid with finding the area of a rectangle and a triangle. What are the similarities and differences? If you make the connections in your mind, you will retain it much better than you would if you memorize the formulas only. IT WILL MAKE SENSE!

23. Assignments Complete the attached exercises.
Then answer the question on the next slide.