Circles: Finding the Area and Circumference

Circles: Finding the Area and Circumference

By LESLEY ELBERT

​Parts of Circles

A circle is a set of all points equidistant to a center.

​

r = radius, d = diameter

​

Diameter: d=2r

​

Radius: ​r= d÷2

Some text here about the topic of discussion

Multiple Choice

What is the diameter?

• 8
• 16
• 10
• 4

Multiple Choice

What is the radius?

• 18
• 72
• 38
• 14

Multiple Choice

What is the diameter of this circle?

• 3.5
• 3
• 5
• 7

Multiple Choice

What is the radius if the diameter is 27?

• 135
• 13.5
• 1.35
• I do not know

Multiple Choice

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

• 12 cm

• 18 cm

• 24 cm

• 6 cm

Finding Circumference and Area

Circumference:

C = πd or C = 2πr

​

Area:

A = πr²

Multiple Choice

Find the circumference of the circle.

• 31.4 cm

• 78.5 cm

• 314 cm

• 15.7 cm

Multiple Choice

Find the circumference of the circle.

• 38.47 cm

• 10.99 cm

• 43.96 cm

• 21.98 cm

Multiple Choice

I wrapped a tape measure around the trunk of the tree and it was 14.13 feet. What is the diameter of the tree? Use 3.14 for pi. Round to the nearest hundredth.

• 2.25 ft

• 44.37 ft

• 4.5 ft

• 17.27 ft

Multiple Choice

Find the area of the circle

• 43.96 units²

• 153.86 units²

• 87.82 units²

• 307.72units²

Multiple Choice

What is the area of this circle?

• 452.39 cm²

• 139.12 cm²

• 113.1 cm²

• 84.23 cm²

Fill in the Blanks

Multiple Choice

A _____ is half of a circle.

• circumference

• pi

• semicircle

• composite figure

Fill in the Blanks

Multiple Choice

A circular apple pie has an area of 706.5 cm². What is the radius of the pie? Use 3.14 for pi.

706.5= $$\pi r^2$$  

• 225 cm

• 112.5 cm

• 15 cm

• 30 cm

Poll

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