How do you find the circumference of a circle?

Finding Circumference

EXAMPLE 1

Find the circumference of the circle to the nearest hundredth. Use 3.14 for .

Step 1: Determine which formula you will use.

Step 3: Substitute the values you know.Step 4: Use order of operations to solve

Step 2: Write it down!

C = dC = (3.14)(9)C = 28.26 in.

EXAMPLE 2

Step 1: Determine which formula you will use.

Step 3: Substitute the values you know.Step 4: Use order of operations to solve

Step 2: Write it down!

C = 2 r

C = 132 ft.

A circular wading pool at a park has a radius of 21 feet. Find the circumference of the pool. Use for .

C = 2( )(21)

EXAMPLE 3A circular concrete patio has a circumference of about 1,000 feet. A gardener placed a palm tree in the center. How far is the tree from the edge of the patio to the plant at the center?

C = 1,000 ftStep 1: Determine which formula you will use.

Step 3: Substitute the values you know.Step 4: Use your mad algebra skills to solve for r !

Step 2: Write it down!

C = 2 r

C = 159.2 ft.

1000 = 2(3.14)r1000 = 6.28r6.28= r1000

6.286.28

CIRCUMFERENCE RACE

1. a circle with diameter 14 mm about 44 mm

Use 3.14 or for . Round to the nearest hundredth, if necessary.

2. a circle with radius 5 in. about 31.40 in.

How do you find the circumference of a circle?Sample answer:Use C = d or C = 2 r, where C is thecircumference, d is the diameter, and r is the radius. Use 3.14 for .