Area of Circle: Radius

Area of a Circle

Calculating the area of a circle

Area of a circle is the amount of space inside the circle.

To calculate area of a circle we multiply 3.14 x radius²

That means we multiply the radius x itself first!

Multiple Choice

Remember that squaring a number (little 2) means multiplying it by itself. What is 3²

• 3

• 6

• 9

Multiple Choice

Remember that squaring a number (little 2) means multiplying it by itself. What is 5²

• 5

• 10

• 25

To calculate area of a circle, multiply the radius (short line) by itself. Then, multiply by 3.14

Multiple Choice

Let's try one! Find the area of this circle:

• 25

• 78.5

• 31.4

• First, square the radius 

• 5 x 5=25

• Then, multiply by 3.14

• 25 x 3.14=

• 78.5

Multiple Choice

find the area of the circle below.

• 100 cm

• 225 cm

• 9 cm

• 28.26 cm

Multiple Choice

What is the area of this circle?

• 201.06 square meters

• 50.24 square meters

• 123.12 square meters

• 25.12 square meters

Multiple Choice

What is the area of this circle?

• 62.59 cm²

• 113.1 cm²

• 18.84 cm²

• 28.26 cm²

Multiple Choice

Find the area.

• $$472.64in^2$$  

• $$144in^2$$  

• $$452.16in^2$$  

• $$167in^2$$  

Multiple Choice

What is the area of this circle?

• 1384.74 $$ft^2$$

• 2142.12 $$ft^2$$

• 5541.77

• 1289.12 $$ft^2$$

Multiple Choice

Find the area of the circle

• 43.96

• 153.86

• 87.82

• 307.72

Multiple Choice

A _______ is a line segment that goes from the center to the edge of a circle.

• radius

• diameter

• circumference

Review of Circles - 7th Grade Math

Vocabulary Review

Multiple Choice

A _______ is a line segment that goes from the center to the edge of a circle.

• radius

• diameter

• circumference

Multiple Choice

A _______ is a line segment that goes from one edge of a circle to the other and passes through the center.

• radius

• diameter

• circumference

Multiple Choice

The _______ of a circle is the distance around the circle.

• radius

• diameter

• circumference

Radius and Diameter Relationship

Multiple Choice

If the radius of a circle is 5, what is the diameter?

• 2.5

• 5

• 10

Find the Circumference

Multiple Choice

If the radius of a circle is 8, what is the diameter?

• 4

• 8

• 16

Multiple Choice

If the diameter of a circle is 10, what is the radius?

• 5

• 10

• 20

Multiple Choice

If the diameter of a circle is 8, what is the radius?

• 4

• 8

• 16

Find the Area of the Circle

Multiple Choice

If the radius is 5, which formula represents the area of a circle?

$$A=\pi r^2$$  

• $$A=\pi5^2$$  

• $$A=\pi10^2$$  

Multiple Choice

If the radius is 8, which formula represents the area of a circle?

$$A=\pi r^2$$  

• $$A=\pi4^2$$  

• $$A=\pi8^2$$  

Great work today!