Area of a Circle

Area of a Circle

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Difference Between Circumference & Area of a Circle

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Circumference of a Circle

 is the distance around a circle

Area of a circle

- is the number of square units inside the circle.

-is the measure of the space or region enclosed inside the circle

How to visualize area of a circle?

Draw a circle on graph paper and count the number of small squares within it.

What is the area of this circle?

A = 28 square units

Find the area of this circle.

Formula to find the Area of a Circle

Word Problem:

Gina and her family are new in the village. Upon designing their house, they decided to put circular windows on it. If a circular window has a radius of 2 meters, what is the area of the glass of the window?

Solution

Multiple Choice

What do you call the number of square units inside a circle?

• volume

• diameter

• circumference

• area

Multiple Choice

What is the formula used in finding the area of a circle?

• $$A=2\pi r$$

• $$A=\pi d$$

• $$A=\pi r^2$$

Multiple Choice

The bottom surface of a circular pond with a radius of of 3.5 m will be tiled. Find the area of the surface that will be tiled.

• $$3.846m^2$$

• $$38.465m^2$$

• $$384.65m^2$$

• $$3846.5m^2$$

Multiple Choice

What is the area of a circular table top if its diameter is 20 centimeters?

• $$3.14cm^2$$

• $$31.40cm^2$$

• $$314cm^2$$

• $$3140cm^2$$

Multiple Choice

The diameter of a circle is 10 cm. How will you find the area of a circle?

• Square the diameter times 3.14

• Divide the diameter by 2 times 3.14

• Multiply the diameter by itself times 3.14

• Divide the diameter by 2 then multiply by itself and times 3.14

Multiple Choice

How will you find the area of a circle?

• Divide the radius by 2 then times 3.14

• Multiply the radius by itself times the value of pi

• Square 3.14 times the radius

• Square the diameter times 3.14

Multiple Choice

Is the red line a radius or diameter of the circle?

• Radius

• Diameter

Multiple Choice

If the diameter of the circle is 20 cm., what is the radius when squared?

• $$10cm^2$$  

• $$100cm^2$$  

• $$200cm^2$$  

• $$400cm^2$$  

Multiple Choice

What is the radius of this circle?

• 18

• 10

• 9

• 8

Multiple Choice

If the diameter of a circle is 50 yards, the radius is _____

• 100 yards
• 25 yards
• 150 yards
• 15 yards

Multiple Choice

Areas are measured in terms of ________.

• cubic units

• degrees

• meter

• square units

Multiple Choice

Ms. Catall is using a compass to find her way out of the woods. The compass has a radius of 4 centimeters. What is the compass's area?

• 49.2 cm²

• 45.6 cm²

• 50.24 cm²

• 55.9 cm²

Multiple Choice

Shring's dining room table is round and has a radius of 4.5 feet. What is the tabletop's area?

• 63.585 ft²

• 68.345 ft²

• 64.585 ft²

• 61.345 ft²

Multiple Choice

Find the area of the circle

• 43.96

• 153.86

• 87.82

• 307.72