Holt Geometry 9-3 Composite Figures Warm Up Find the area of each figure. 1. a rectangle in which b = 14 cm and h = 5 cm 2. a triangle in which b = 6 in. and h = 18 in. 3. a trapezoid in which b 1 = 7 ft, b 2 = 11 ft, and h = 3 ft A = 70 cm 2 A = 54 in 2 A = 27 ft 2

Holt Geometry 9-3 Composite Figures 9-3 Composite Figures Holt Geometry

9-3 Composite Figures A composite figure is made up of simple shapes, such as triangles, rectangles, trapezoids, and circles. To find the area of a composite figure, find the areas of the simple shapes and then use the Area Addition Postulate.

Holt Geometry 9-3 Composite Figures area of the rectangle: area of triangle: shaded area: A = bh = 20(14) = 280 mm 2 50 ≈ mm 2 area of half circle: Find the shaded area.

Holt Geometry 9-3 Composite Figures

Holt Geometry 9-3 Composite Figures Example 2: Finding the Areas of Composite Figures by Subtracting Find the shaded area. Round to the nearest tenth, if necessary. area of a triangle: area of the half circle: area of figure: Subtract the area of the half circle from the area of the triangle. 234 –  ≈ ft 2

Holt Geometry 9-3 Composite Figures To estimate the area of an irregular shape, you can sometimes use a composite figure. First, draw a composite figure that resembles the irregular shape. Then divide the composite figure into simple shapes.

Holt Geometry 9-3 Composite Figures Check It Out! Example 4 Use a composite figure to estimate the shaded area. The grid has squares with side lengths of 1 ft. Draw a composite figure that approximates the irregular shape. Find the area of each part of the composite figure.

Holt Geometry 9-3 Composite Figures Check It Out! Example 4 Continued area of triangle: area of half circle: area of rectangle: A = lw = (3)(2) = 6 ft 2 The shaded area is about 12 ft 2.

Holt Geometry 9-3 Composite Figures

Holt Geometry 9-3 Composite Figures Lesson Quiz: Part I 38.6 cm 2 Find the shaded area. Round to the nearest tenth, if necessary ft 2

Holt Geometry 9-3 Composite Figures Lesson Quiz: Part II $ Mike is remodeling his kitchen. The countertop he wants costs $2.70 per square foot. How much will Mike have to spend on his remodeling project?

Holt Geometry 9-3 Composite Figures Lesson Quiz: Part III about 8.5 cm 2 4.Use a composite figure to estimate the shaded area. The grid has squares with side lengths of 1 cm.

Holt Geometry 9-3 Composite Figures Warm-Up $ Mike is remodeling his kitchen. The countertop he wants costs $2.70 per square foot. How much will Mike have to spend on his remodeling project?