# 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

## PRACTICE IT Perimeter of Shapes Composed of Rectangles

## Beginning

Extend your knowledge of rectangles to finding the perimeter of shapes composed of rectangles. Composite Shapes Experienced ALL

## Experienced

Find the perimeter of various compound shapes and the circumference of partial circles. Exploring Perimeter.pdf

All my perimeter tricks in one place: estimation, math reasoning, composite shapes

Example 1

Example 2

Example 3

Example 4

Example 5

Challenge 1

Challenge 2