1. 11.2 Areas of Parallelograms and Triangles
Objective: After studying this section you will be able to find the areas of parallelograms and triangles

2. The Area of a Parallelogram
We can “cut and paste” to find the area of a parallelogram.
base (b)
height (h)
cut
paste =

3. Theorem. The area of a parallelogram is equal to the
Theorem The area of a parallelogram is equal to the product of the base and the height for that base.
where b is the length of the base and h is the height

4. The Area of a Triangle
The area of any triangle can be shown to be one half of the area of a parallelogram with the same base and height
Theorem The area of a triangle is equal to one-half the product of a base and the height (or altitude) for that base.
where b is the length of the base and h is the altitude.

5. Example 1 Example 2 Find the area of the triangle 15 cm 10 cm 8 mm

6. Example 3
Find the base of a triangle with altitude 15 and area 60. (Hint: draw a picture)
Example 4
Find the area of a parallelogram whose sides are 14 and 6 and whose acute angle is 60 degrees. (Hint: draw a picture).

7. Example 5
Find the area of trapezoid (use formulas you learned in this lesson). 12 13 15 18

8. Summary
State in your own words how you can find the area of a parallelogram and a triangle.
Homework: worksheet