Area of a Circle and Parts of a Circle

Area of a Circle and Parts of a Circle

By Kevvin Hankins

Parts of a Circle

Multiple Choice

It is the distance around the circle. The "perimeter" of the circle.

• Chord

• Diameter

• Circumference

• Radius

Multiple Choice

It is the distance from the center to any point in the circle.

• Circumference

• Diameter

• Segment

• Radius

Multiple Choice

It is an area enclosed by a chord and an arc

• Tangent

• Segment

• Sector

• Diameter

Multiple Choice

It is an area enclosed by two radii and an arc

• Tangent

• Segment

• Sector

• Diameter

Multiple Choice

It is a straight line outside the circle that touches the circumference at one point

• Segment

• Chord

• Radius

• Tangent

Multiple Choice

It is a part of the circumference of any circle

• Arc

• Chord

• Radius

• Diameter

Multiple Choice

It is the distance across the circle that passes through the center

• Radius

• Diameter

• Circumference

• Chord

Multiple Choice

It is a straight line that touches two points of the circumference but does NOT pass through the center

• Radius

• Diameter

• Circumference

• Chord

Circumference and Area of a Circle

Circle

The set of points equidistant from a given point called the center

Parts of a Circle

Circumference - the distance around the circle

Diameter - the distance across the circle, through the center

Radius - The distance from the center to any point on the circle

Multiple Choice

What does the red line represent?

• The circumference of the circle

• The diameter of the circle

• The radius of the circle

Radius and Diameter

The diameter is twice as long as the radius.

d = 2r

The radius is half the length of the diameter.

r = d/2

Multiple Choice

The diameter of a circle is 10 in.

What is its radius?

• 20 in.

• 5 in.

Pi

The ratio of a circle's circumference to its diameter.

Used to calculate the circumference and area of a circle.

Multiple Choice

Which ratio is used to calculate Pi?

• C/r

• C/d

• r/C

• d/C

Solve for C

Circumference

Solve a Circumference Problem

1. Write the formula

2. Substitute the values

3. Multiply

4. Write the unit of measure

Multiple Choice

Calculate the circumference of the circle.
C =  $$\pi$$  d

• 98.91 ft.

• 63 ft.

• 197.82 ft.

Given a circle with a diameter of 63 ft.

calculate the circumference

Area of a Circle

Solve an Area of a Circle Problem

Multiple Choice

Does this circle show the radius or diameter?

• radius

• diameter

Multiple Choice

According to the Area of a Circle formula, do you need to know the radius or diameter?
A =  $$\pi$$   $$r^2$$  

• radius

• diameter

Multiple Choice

What is the radius of this circle?

• 40 cm

• 20 cm

• 10 cm

Multiple Choice

Calculate the Area of the circle.

A =  $$\pi$$   $$r^2$$  

• 314 $$cm^2$$

• 62.8  $$cm^2$$  

• 1256  $$cm^2$$  

Given a circle with a diameter of 20 cm.

calculate the area.