Area and Circumference

Area & Circumference

Circumference of a Circle

This is the perimeter of a circle

Calculating circumference using your calculator

​Find the circumference of a circle with a radius of 9cm.

Calculating circumference using your calculator

​Find the circumference of a circle with a radius of 9cm.

Calculating circumference using your calculator

​Find the circumference of a circle with a radius of 9cm. Round to the nearest tenth.

Step 1: Decide what formula you want to use.

Calculating circumference using your calculator

​Find the circumference of a circle with a radius of 9cm. Round to the nearest tenth.
Step 2: Type values into your calculator correctly.

Calculating circumference using your calculator

​Find the circumference of a circle with a radius of 9cm. Round to the nearest tenth.
Step 3: Write your answer and round accordingly.

Multiple Choice

What is the circumference for a circle with a radius of 9 cm? Round to the nearest tenth.

• 56.5 cm

• 28.3 cm

• 3.1 cm

• 9 cm

In terms of pi??

Sometimes a problem will ask for area/circumference in terms of pi. This means that pi is in your answer. For example...
Find the circumference of a circle in terms of pi that has a diameter of 12 feet.
C=πd
C=12π - Done!!

Multiple Choice

What is the circumference of a circle with a diameter of 18 feet in terms of pi?

• 18π

• 9π

• 56.55 feet

• 28.27 feet

Area of a Circle

This is how much space a circle takes up.

Calculating area using your calculator

Find the area of a circle with a radius of 5.5 inches. Round to the nearest whole number.
Step 1: Figure out if you are given the diameter or the radius and modify the value if needed.

Calculating area using your calculator

Find the area of a circle with a radius of 5.5 inches. Round to the nearest whole number.
Step 2: Simplify the values before putting them in the calculator or make sure you are putting them in the calculator correctly.

Calculating area using your calculator

Find the area of a circle with a radius of 5.5 inches. Round to the nearest whole number.
Step 3: Write down your answer and round correctly.

Multiple Choice

What is the area of a circle with a radius of 5.5 inches? Round to the nearest whole number.

• 95 in²

• 17 in²

• 5.5 in²

• 3.14 in²

Multiple Choice

What is the area of a circle that has a diameter of 12 feet in terms of pi?

• 6π

• 12π

• 36π

• 144π