L-shaped garden
Here's an L-shaped garden. How can we find its area when it's not a simple rectangle?
Here's our shape — an L. It's called a composite polygon because it's made of simpler shapes joined together.
Let's mark the side lengths. The top is 3 meters, that side drops 4 meters, the bottom runs 8 meters across, and the right side is 3 meters tall.
Here's our trick: split this L into two rectangles, find each area, and add them up.
We'll cut along this line, separating a top rectangle from a bottom rectangle.
Look at rectangle A on top. It's 3 meters wide and 4 meters tall.
Area equals length times width. Three times four is twelve square meters.
Now rectangle B on the bottom. It stretches the full 8 meters across and 3 meters tall.
Eight times three is twenty-four square meters.
Now add the two pieces. Twelve plus twenty-four is thirty-six.
The L-shape has an area of thirty-six square meters. Decompose, calculate, add — that's the recipe!
Now you try. Find the area of this figure. What is the area?