Area of composite figures, step by step
A composite figure has no formula of its own, and that is the point.
The question
cm²
Area of a 19 by 19 L-shape
- First way: pretend the bite was never taken. The whole rectangle would be 19 × 19 = 361.
- Then take the bite off. It is 7 × 6 = 42, so the L is 361 − 42 = 319 square cm.
- Second way, and it works on any of these: cut the L into two rectangles.
- The bottom strip is 19 × 13 = 247, and the piece standing on it is 12 × 6 = 72.
- 247 + 72 = 319 square cm — the same answer as the first way. Two methods that agree is how you know the answer is right.
How it works.
- 01
First way: pretend the bite was never taken. The whole rectangle would be 19 × 19 = 361.
- 02
Then take the bite off. It is 7 × 6 = 42, so the L is 361 − 42 = 319 square cm.
- 03
Second way, and it works on any of these: cut the L into two rectangles.
- 04
The bottom strip is 19 × 13 = 247, and the piece standing on it is 12 × 6 = 72.
- 05
247 + 72 = 319 square cm — the same answer as the first way. Two methods that agree is how you know the answer is right.