1. Opening Activity 1. Find the area of a circle with a radius of 5 cm. A=(3.14)(5)(5) 2. What is the area of a semicircle with radius of 14 yd?

2. Chapter 8 Lesson 3 Area of Composite Figures

3. Objective: Students will find the area of composite figures.

4. A composite figure is made up of two or more shapes. To find the area of a composite figure, decompose (or take apart) the figure into shapes with areas you know. Then find the sum of these areas. ShapeWordsFormula ParallelogramArea is the product of any base b and its height h A=bh TriangleArea is half the product of any base b and its height h TrapezoidArea A is half the product of the height h and the sum of the bases b1 and b2. CircleArea is equal to pi times the square of the radius

5. Example 1: State what two shapes make up these composite shapes. parallelogram rectangle triangletrapezoid semicircle rectangle

6. Example 2: Find the area of the figure. Round to the nearest tenth if necessary. 12 cm 6cm There are two shapes present in this figure, a semicircle and a rectangle so we will need to use two area formulas and then add the two areas together : Area of a semicircle: Area of a rectangle: A=lw Semicircle:Rectangle:A=(12)(6) Area of the composite figure = 14.13 + 72= 86.13

7. Example 3: Pedro’s father is building a shed. How many square feet of wood are needed to build the back of the shed shown? 4ft 12ft 15ft Triangle: rectangle: A=lw A=(12)(15) To find the total area of the composite shape, add the two areas together. A = 30 + 180 So Pedro’s father will need 210 square feet of wood to build the back of the shed.

8. You can use the areas you know to find the area of a shaded region. Example 4: Two congruent triangles are cut from a rectangle. Find the area of the shaded region. Round to the nearest tenth if necessary. 8i n 6in Rectangle: A=lw A=(16)(12) Triangle: Multiply by 2 because there are 2 triangles. To find the total area of the composite figure, subtract the area of the triangles from the area of the rectangle. A= 192 - 48 So the area of the blue shaded region is 144 square inches.

9. Example 5: A diagram for a park is shown. The shaded area represents the picnic sections. Find the area of the picnic sections. 150 yd 25 yd 60 yd 50 yd 120 yd Rectangle: A=lw A=(25)(60) Triangle: b=150-120=30 yd To find the area of the blue picnic section, add the area of the triangle to the area of the rectangle. A = 1500 + 750 The area of the picnic section is 2,250 square yards.