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AREA OF COMPOSITE FIGURES. COMPOSITE FIGURES A composite figure is made of triangles, quadrilaterals, semicircles, and other 2-D figures. A semicircle.

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Presentation on theme: "AREA OF COMPOSITE FIGURES. COMPOSITE FIGURES A composite figure is made of triangles, quadrilaterals, semicircles, and other 2-D figures. A semicircle."— Presentation transcript:

1 AREA OF COMPOSITE FIGURES

2 COMPOSITE FIGURES A composite figure is made of triangles, quadrilaterals, semicircles, and other 2-D figures. A semicircle is half of a circle. Examples: SEMICIRCLE RECTANGLE TRAPEZOID TRIANGLE To find the area of a composite figure, separate it into figures with areas you know how to find. Then add those areas.

3 Let’s find the area of the following composite figure. AREA OF COMPOSITE FIGURES 6 cm 3 cm 14 cm This figure can be separated into a rectangle and a semicircle. Now we just find the area of each figure. AREA OF RECTANGLE: A = lw A = 14  3 A = 42 cm 2 AREA OF SEMICIRCLE: A =  r 2 ( this is area of a 2 circle, cut in ½) A = 3.14  4  4 2 A = = cm 2 2 BOTH AREAS ADDED TOGETHER: = cm 2

4 Now you try to find the area of the following composite figure. AREA OF COMPOSITE FIGURES This figure can be separated into a triangle and ¾ of a circle. Now we just find the area of each figure. AREA OF TRIANGLE: A = bh 2 A = 12  3 2 A = 36 = 18 cm 2 2 AREA OF CIRCLE: A =  r 2 (this is area of a WHOLE circle) A = 3.14  3  3 A = cm 2 (WHOLE CIRCLE) Now, we only need area for 3 parts of the circle ; so we need to divide the area by 4 to get ¼ then multiply by 3 to get ¾ ÷ 4 =  3 = cm 2 is ¾ of circle. 3 cm 12 cm Together: = cm 2 for the area of the composite figure.

5 Now you try again to find the area of the following composite figure. AREA OF COMPOSITE FIGURES This figure can be separated into a square & a rectangle. Now we just find the area of each figure. AREA OF SQUARE: A = side  side A = 3  3 A = 9 cm 2 AREA OF RECTANGLE: A = bh A = 12  3 A = 36 cm 2 3 cm Together: = 45 cm 2 for the area of the composite figure. 9 cm 12 cm 6 cm

6 Sometimes you have to find the area of the shaded region in each figure. o This figure is a large circle with a small circle inside it. o To find the area of just the shaded part (the outer circular part), o we need to find the area of both the larger circle and the smaller o white filled circle, and then subtract the two areas to get just the shaded circle’s area. AREA OF SHADED PARTS OF FIGURES AREA OF LARGE CIRCLE: A =  r 2 A = 3.14  4  4 A = m 2 8 m 6 m AREA OF SMALL CIRCLE: A =  r 2 A = 3.14  3  3 A = m 2 Now, we take the 2 areas and subtract: – = m 2

7 Now you try o This figure is a large circle inside a square. o Find the area of only the rectangle part showing around the circle. AREA OF SHADED PARTS OF FIGURES AREA OF CIRCLE: A =  r 2 A = 3.14  6  6 A = m 2 12 m 6 m AREA OF SQUARE: A = s 2 A = 12  12 A = 144 m 2 Now, we take the 2 areas and subtract: – = m 2


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