Perimeter of Composite Shapes
When the Formulas Fail
On the GED, you may encounter shapes where the formula sheet appears to fail. Perimeter of an "ice cream cone shape"? Perimeter of an "L-shape"? Neither is on the formula sheet. In cases like this, don't panic. Remember that the perimeter can always be found by adding up all the outer sides of a shape.
LEARN IT
Remember that perimeter is defined as "the distance around a 2-dimensional shape". Whether you are finding the perimeter of known shapes, like a triangle, or unknown shapes, you can always total the lengths of all the sides in order to get perimeter.
To find the perimeter of composite shapes:
Make sure every side-length is labeled with a length
To find missing lengths, use the properties of the composite shape in order to find missing side lengths.
Total the side lengths
Watch the Virtual GED Class video below for a complete explanation and tons of worked example problems. Refer to your GED Formula sheet and print out the example problems to follow along with the video lesson.
PRACTICE IT
Extend your knowledge of rectangles to finding the perimeter of shapes composed of rectangles.
Find the perimeter of various compound shapes and the circumference of partial circles.
Exploring Perimeter.pdfAll my perimeter tricks in one place: estimation, math reasoning, composite shapes
WORKED EXAMPLES
Example 1
Example 2
Example 3
Example 4
Example 5
Challenge 1
Challenge 2
Advanced
