Area and Circumference of a Circle

Area and Circumference of a Circle

Terms, Values, and Formulas to Remember

• Radius - a straight line from the center to the circumference of a circle

• Diameter - a straight line passing from side to side through the center of a circle

• Diameter is twice the radius, i.e.,  $d=2\cdot r$  

•  $\pi=3.14$  
  

• Area of a Circle: $\pi\cdot r^2$  
  

• Circumference of a Circle:  $2\pi r$  or  $\pi\cdot d$  

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 $\pi=$  

Multiple Choice

What formula can be used to find the circumference of a circle?

• $A=b\cdot h$

• $A=\pi\cdot r^2$

• $C=\pi\cdot d$

Multiple Choice

What formula can be used to find the circumference of a circle?

• $$A=\pi\cdot r^2

•  $C=2\pi\cdot r$ 
  

•  $A=b\cdot h$  
  

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What is the circumference of the circle shown? Round your answer to the nearest tenths place.

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What is the circumference of the circle shown? Round your answer to the nearest tenths place.

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The circumference of a circle is 37.68 feet. What is the radius of the circle?

Multiple Choice

What formula can be used to find the area of a circle?

• $A=b\cdot h$

• $A=\pi\cdot r^2$

• $A=\frac{1}{2}b\cdot h$

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What is the area of the circle shown? Round your answer to the nearest tenths place.

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What is the area of the circle shown? Round your answer to the nearest tenths place.

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CHALLENGE PROBLEM! A pulley has many uses in mechanics and is measured by its diameter. If a 10 inch pulley spins a belt that is 84 inches long. How many rotations of the pulley does it take to turn the belt over once? Round your answer to the nearest tenth of a rotation.

Multiple Choice

CHALLENGE PROBLEM! Two pizza chains claim they are the cheesiest. 

Hugo's uses 6 ounces of cheese on their personal sized pizzas with an area of 201 square inches. 

DeLorenzo's also uses 6 ounces of cheese on their personal sized pizzas and they have a circumference of 47.1 inches.

Which pizza chain has the most cheese given its area?

• Hugo's

• DeLorenzo's