During this lesson, you will: Estimate the area of irregular shapes Decompose irregular polygons into squares, rectangles, triangles, and other familiar shapes Determine the area of an irregular polygon by summing the areas of its composite shapes

Area = ___________________________

Area = __________________________

Area (rect./square) = __________________

Area = __________________________

Area = __________________________

bh*bh*bh h* (b1 + b2) r2

KEY to Irregular Figure AreasTo find the area of an irregular figure:Divide the figure into familiar geometric figures.Use known measures (and parallel sides) to determine unknown measures. Find the area of each familiar shape. ADD the sum of the areas of each shape to find the total area.

Method:Divide and Conquer

Divide each figure below 2 different ways. B. Find missing dimensions. C. Find each area. D. Find total area.20 cm5 cm5 cm5 cm5 cm4cm4cm4cm4cm5 cm5 cm5 cm5 cm4cm4cm4cm4cm20 cm240 cm260 cm280 cm280 cm260 cm240 cm220 cm2200 cm2

Find the area of the figure to the nearest tenth, if necessary.4 cm4 cm12 cm+=A = bhA = bh60 cm2

KEY to Irregular FigureAreasFind the area of each shaded region.Method:Area (larger) Area (smaller)28 cm15 cm5 cm10 cmA = bhA = bh370 cm2

KEY to Irregular Figure AreasMethod:Area (larger) Area (smaller)3 cm6 cm11 cm3 cm6 cm3 cm3cmA = bh

A = bh-51 cm2

KEY to Irregular Figure AreasMethod:Area (larger) Area (smaller)Find the area of the shaded region.R = 12 cm;r =8 cmA = r2A = r2Answer: 80 cm2-

Final Checks for Understanding

In your own words, summarize a general technique for finding areas of irregular figures.Absent? Check out this link on irregular areas:

Final Checks for UnderstandingFind the area of the shaded region.120 cm2104 cm2110 cm2

Homework Assignment Area: Irregular Figures WS, plus textbook: