Perimeter of a composite figure is the total length of its continuous outer boundary, found by identifying and adding every exterior side, including sides whose lengths must be inferred from aligned segments, equal lengths, or the dimensions of component rectangles and other polygons. Interior shared edges are not included; lengths are expressed in consistent units, and the reasoning supports geometric decomposition and later algebraic work with unknown dimensions.
The perimeter is the distance around the entire outside boundary of a figure. Add each exterior side once. Do not include edges inside the figure where two rectangles share a side.
Consider this L-shaped figure:
6 cm
┌──────┐
│ │
│ │
│ └──────┐
│ │ 3 cm
└─────────────┘
10 cm
The total height on the left is cm.
Step 1: Find the missing vertical side.
The whole height is cm. The lower vertical section is cm, so the upper vertical section is
Step 2: Find the missing horizontal side.
The whole width along the bottom is cm. The top horizontal section is cm, so the missing middle horizontal section is
Step 3: Add every outside side.
Trace around the boundary and add:
Therefore,
The perimeter of the composite figure is .
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