Composite plane figures

Split a composite shape into familiar pieces, or subtract a missing piece from a larger shape. Use each area once. For perimeter, return to the original boundary instead of adding the perimeters of the pieces.

Example

An L-shape is made by cutting a \(6\text{ cm}\) by \(4\text{ cm}\) rectangle from the top-right corner of a \(12\text{ cm}\) by \(8\text{ cm}\) rectangle. Its area is \(12\times8-6\times4=72\text{ cm}^2\). Its boundary lengths are 12, 4, 6, 4, 6 and 8 cm, totalling \(40\text{ cm}\).

If a semicircle of radius 3 cm is attached along its diameter to a rectangle, the joined diameter is internal. The new curved boundary is \(3\pi\text{ cm}\), not the semicircle perimeter \(3\pi+6\). Draw a finger around the exposed outline to decide which straight segments remain.