Pre-Algebra : Circumference of a Circle

Study concepts, example questions & explanations for Pre-Algebra

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Example Questions

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Example Question #1 : Perimeter

Becky's house is surrounded by a circular lake that Becky runs around each day. If Becky wants to figure out the distance she runs around the lake, what formula should Becky use?

Possible Answers:

None of the other answers

Correct answer:

Explanation:

 

Becky should use the circumfrence formula to find the distance she runs of a lake.

Correct Answer:

Example Question #1 : Perimeter

What is the circumference of a circle with an area equal to ?

Possible Answers:

Correct answer:

Explanation:

Using the area, solve for the radius:

Divide by :

Take the square root:

Plug this radius into the formula for the circumference:

Example Question #2 : Perimeter

What is the circumference of a circle with a radius equal to ?

Possible Answers:

Correct answer:

Explanation:

The circumference can be solved using the following equation:

Example Question #196 : Geometry

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

Possible Answers:

Correct answer:

Explanation:

The circumference can be solved using the following equation:

Where  represents the radius. Therefore, when we substitute our radius in we get:

Example Question #197 : Geometry

The perimeter of a given rectangle is equal to the circumference of a given circle. The circle has radius  inches; the width of the rectangle is  inches. What is the length of the rectangle?

Possible Answers:

 inches

 inches

 inches

 inches

 inches

Correct answer:

 inches

Explanation:

The circumference of a circle with radius  inches is 

 inches.

The perimeter of the rectangle is therefore  inches. To find its length, substitute  and  into the equation and solve for :

 inches

Example Question #3 : Perimeter

Determine the circumference of the circle if the radius is 20.

Possible Answers:

Correct answer:

Explanation:

Write the formula for circumference.

Substitute the radius and solve.

Example Question #4 : Perimeter

Given the area of the circle is , what is the circumference of the circle?

Possible Answers:

Correct answer:

Explanation:

Write the formula for the area of a circle.

Substitute the area.

Write the circumference of the circle.

Substitute the radius.

Example Question #5 : Perimeter

Find the circumference of a circle with an area of .

Possible Answers:

 

Correct answer:

 

Explanation:

Write the area formula in order to find the radius.

Substitute the area.

Write the circumference formula.

Substitute the radius.

Example Question #6 : Perimeter

Determine the circumference of the circle if the radius is .

Possible Answers:

Correct answer:

Explanation:

Write the formula for the circumference of a circle.

Substitute the radius into the formula.

Example Question #7 : Perimeter

Find the circumference of a circle with a radius of .

Possible Answers:

Correct answer:

Explanation:

Write the formula to find the circumference of a circle.

Substitute the radius.

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