Area & Circumference of Circles

Area & Circumference of Circles

Dr. Tom Giles

​Math Antics Circles, Circumference, & Area

The area of a circle is equal to the radius of the circle squared times pi.

​​Area Formula

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The circumference of a circle is equal to the diameter of the circle times pi or the radius times two multiplied by pi.

​​Circumference Formula

Multiple Choice

What is the circumference of a circle with diameter 10cm?

• 10π cm

• 20π cm

• 5π cm

• 100π cm

Multiple Choice

What is the circumference of a circle with radius 6cm?

• 12π cm

• 36π cm

• 18π cm

• 6π cm

Multiple Choice

A circular table has a radius of 1.5m. What is the circumference of the table to the nearest meter?

• 9m

• 3m

• 4m

• 7m

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Multiple Choice

What is the circumference of a circle with diameter 18cm?

• 18π cm

• 9π cm

• 36π cm

• 28π cm

Multiple Choice

A circular garden has a radius of 5m. How many meters of fencing would be needed to surround the garden completely?

• 10π m

• 15π m

• 25π m

• 50π m

Multiple Choice

What is the formula for the area of a circle with radius r?

• A = 2πr
• A = πr^2
• A = πd
• A = 2r

Multiple Choice

What is the area of this circle?

• 4π

• 8π

• 16π

• π

Multiple Choice

A circular rug has a radius of 2.5m. What is the circumference of the rug to the nearest meter?

• 16m

• 5m

• 8m

• 20m

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Multiple Choice

What is the area of a circle with diameter 14cm?

• 49π cm^2

• 196π cm^2

• 98π cm^2

• 28π cm^2

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Multiple Choice

What is the area of a circle with radius 8cm?

• 16π cm^2
• 64π cm^2
• 128π cm^2
• 32π cm^2

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Multiple Choice

A pizza has a diameter of 20cm. What is the area of the pizza to the nearest square centimeter?

• 314 cm^2

• 201 cm^2

• 100 cm^2

• 1256 cm^2

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Multiple Choice

A circular fountain has a diameter of 8m. What is the area of the water surface to the nearest square meter?

• 50m^2
• 201m^2
• 100m^2
• 25m^2

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Multiple Choice

What is the area of a circle with radius 3cm?

• 3π cm^2
• 6π cm^2
• 9π cm^2
• π cm^2

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Multiple Choice

A circular pond has a radius of 12m. What is the circumference of the pond to the nearest meter?

• 38m
• 24m
• 75m
• 48m

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Multiple Choice

A circular pool has a diameter of 6m. What is the area of the pool to the nearest square meter?

• 28m^2

• 9m^2

• 3m^2

• 12m^2

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Multiple Choice

A circular trampoline has a diameter of 4.5m. What is the area of the trampoline to the nearest square meter?

• 16m^2
• 6m^2
• 64m^2
• 32m^2

Fill in the Blanks

Multiple Choice

What is the formula for the circumference of a circle with radius r?

• C = 2πr
• C = πr^2
• C = πd
• C = 2r

Fill in the Blanks