Composite Figures (Addition and Subtraction)

The ground covered by a shape joining a quadrilateral with part of a circle is assembled by adding and subtracting. A roof shape with a semicircle on a square, a shape with a semicircle at each end of a rectangle, shapes with corners cut away by quarter circles, a ring shape and more, eight drawings in all, come as calculation.

In a Stadium Shape with a semicircle at each end, the two together make one whole circle. Where corners are cut away by quarter circles, two together make one semicircle. Counting first how many curved parts the drawing has and what fraction of a circle each is finds an expression that added or subtracted only half of one.

Practice finding the ground part by part ran to Area of Semicircles and Sectors, and here those parts become the material for assembly. In Composite Figures (Overlap and Difference) the same adding and subtracting goes one level deeper, to pull out the overlapping part itself.