Perimeter of Composite Figures w/Circles

Let’s review circumference

Circumference is the perimeter of a
circle

Two formulas to find circumference:

C = πd

Or

C = 2πr

What happens if we need to find perimeter of this shape?

A circle and a rectangle make up this figure.

Two semicircles make 1 whole circle

Two steps to find perimeter

1. Find circumference
2. Add in the other 2

sides

What does this look like?

1. Find circumference

C = πd

C = π x 5 = 15.71 ft

2. Add in the other 2 sides
3. 15.71 + 7 + 7 = 29.71 ft

Let's find perimeter of this figure.

Step 1:

Find Circumference -

C = πd

C = π x 4

C =

To find circumference....

Step 1:

Find Circumference -

C = πd

C = π x 4

C = 12.57 cm

Find Perimeter - the steps

Step 1:

Find Circumference -

C = πd

C = π x 4

C = 12.57 cm
Step 2 - add the other sides to circumference.
12.57 + 7 +7 = 29.57 cm

Let’s do that again - Find Perimeter by first finding Circumference.

Step 1:

Find Circumference -

C = πd

C = π x 4

C =

Next, add the sides to the circumference. What is the perimeter?

Step 2 - add the sides to the
circumference.

12.57 + 5 + 5

Perimeter =

What is the perimeter of this figure?

Remember the steps:

1. Find circumference

C = πd

C = π x 4 = _____

2. Add in the other 2 sides