Area and circumference of a circle

The area and circumference of a circle

What is Pi?

• The ratio between circumference and diameter

• A never-ending non-repeating irrational number (cannot be written as a fraction)

• A Greek symbol (π)

• Approximately 3.14

• Used when solving the area and circumference of circles

Multiple Select

What is pi?

Check ALL applicable answers!

• a delicious dessert

• the ratio between circumference and diameter

• a Greek symbol

• exactly 3.14

• approximately 3.14

The Center

• The midpoint in the diameter

• The point that is equidistant (equally far) from all points in a circle

​The diameter is TWICE the radius

It goes from one side of the circle to the other

​The radius is HALF of the diameter!

Multiple Choice

Name the pictured part of the circle.

• Diameter

• Sector

• Radius

• Central Angle

• Arc

Multiple Choice

What is a straight line that goes through the center of a circle from side to the opposite side?

• Diameter

• Circumference

• Radius

• Center

Multiple Choice

Does this picture show the diameter or radius of a circle?

• Diameter

• Radius

Multiple Choice

A tire has a radius of 14 inches. What is its diameter?

• 14 inches

• 7 inches

• 28 inches

Fill in the Blank

What is the length of the radius of the circle?

Multiple Choice

A pond has a diameter of 12 feet. What is its radius?

• 12 feet

• 6 feet

• 24 feet

Circumference & Area of a circle formulae

Circumference

the distance around the outside of a circle (AKA perimeter)

Multiple Choice

The distance around a circle; is much like the perimeter of a rectangle.

• perimeter

• diameter

• circumference

• radius

Continue clicking through the next slides to view an example on finding the circumference of a circle when given the radius.

After the guided example, you will try one on your own!

Now, you will try one on your own!

Fill in the Blank

Find the circumference of the circle.

Type your answer as _____ m

Sample: 3.14 m

.

Now, continue clicking through the next slides to view an example on finding the circumference of a circle when given the diameter.

After the guided example, you will try one on your own!

Fill in the Blank

Find the circumference of the circle.

Type your answer as _____ ft

Sample: 3.14 ft

.

Fill in the Blank

A cruise ship has a large, circular window with a diameter of 6 meters. What is the window's circumference?

(Round to the hundredths)

Area

• the measure inside the circle

• always in square units

Multiple Choice

What is the area of this circle?

• 28.26 cm²

• 28.26 cm

• 9.42 cm²

• 9.42 cm

Multiple Choice

What is the area of this circle?

• 28.26 in²

• 56.52 in²

• 254.34 in²

Multiple Choice

What is the area of this circle? Round to the nearest tenths place.

• 452.2 cm²

• 113.1 cm²

• 37.7 cm²

Multiple Choice

What is the diameter of this circle?

• 3.7 m

• 74 m

• 4 m

• 7.4 m

Multiple Choice

What is the radius of this circle?

• 13 ft

• 6.5 ft

• 26 ft

• 7.5 ft

Multiple Choice

If the the diameter of the large circle is 36 cm, what is the radius of each of the small circles?

• 12 cm

• 24 cm

• 18 cm

• 6 cm

Fill in the Blank

Find the circumference of the circle.

Type your answer as _____ ft

Sample: 3.14 ft

.

Fill in the Blank

Find the circumference of the circle.

Type your answer as _____ in

Sample: 3.14 in

.

Fill in the Blank

The radius of the circle is 9 meters. What is the circle's circumference?