GED Math : Area of a Circle

Study concepts, example questions & explanations for GED Math

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Example Questions

Example Question #116 : 2 Dimensional Geometry

Sector40

The figure above is a circle.

If the radius of the circle above is 9 in., what is the area of the sector? Round to the nearest hundredth.

Possible Answers:

 

 

 

 

 

Correct answer:

 

Explanation:

To find the area of a sector, you are looking for a percentage of the total circle's area.  Thus, if the angle is  degrees, you are looking for  of a complete circle. 

Given that the radius is  in., you know that the area must be:

The area of the sector is:

or

Example Question #117 : 2 Dimensional Geometry

Sector77

The figure above is a circle.

If the diameter of the circle above is 10 in., what is the area of the sector? Round to the nearest hundredth.

Possible Answers:

 

 

 

 

 

Correct answer:

 

Explanation:

To find the area of a sector, you are looking for a percentage of the total circle's area.  Thus, if the angle is  degrees, you are looking for  of a complete circle. 

Given that the diameter is  in., you know that the radius is  in.  This means that the area must be:

The area of the sector is:

or

Example Question #118 : 2 Dimensional Geometry

Find the area of a circle with a radius of 8in.

Possible Answers:

Correct answer:

Explanation:

To find the area of a circle, we will use the following formula:

where r is the radius of the circle. 

Now, we know the radius of the circle is 8in. So, we can substitute. We get

Example Question #119 : 2 Dimensional Geometry

Determine the area of a circle with an diameter of .

Possible Answers:

Correct answer:

Explanation:

Write the formula for the area of a circle.

The radius is half the diameter.

The answer is:  

Example Question #121 : 2 Dimensional Geometry

Find the area of a circle with a diameter of .

Possible Answers:

Correct answer:

Explanation:

Write the formula for the area of a circle.

The radius is half the diameter.

Multiply the diameter by .

Substitute the radius.

The answer is:  

Example Question #122 : 2 Dimensional Geometry

Find the area of a circle with a diameter of .

Possible Answers:

Correct answer:

Explanation:

Write the area of a circle.

The radius is half the diameter.

Substitute the radius into the equation.

The answer is:  

Example Question #123 : 2 Dimensional Geometry

Circle 1

Give the area of the above circle.

Possible Answers:

Correct answer:

Explanation:

The area  of a circle, given its radius , can be found using the formula

The radius is half the diameter - that is,  - so, substituting, 

or

The diameter of the given circle is 7, so set  in the above formula:

,

the correct area.

Example Question #124 : 2 Dimensional Geometry

Let .

Find the area of a circle with a diameter of 12in.

Possible Answers:

Correct answer:

Explanation:

To find the area of a circle, we will use the following formula:

where r is the radius of the circle. 

Now, we know . We also know the diameter is 12in. We know the diameter is two times the radius, so the radius is 6in. Now, we can substitute. We get

Example Question #121 : Circles

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

Possible Answers:

Correct answer:

Explanation:

Write the formula for the area of a circle.

We will need to find the radius of the circle.

Write the formula for the circumference.

Substitute the circumference.

Divide by  on both sides.

The radius is:  

Substitute this into the area formula.

The answer is:  

Example Question #126 : 2 Dimensional Geometry

Find the area of the circle with radius of .

Possible Answers:

Correct answer:

Explanation:

Write the formula for the area of a circle.

Substitute the radius.

The answer is:  

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