GED Math : Area of a Circle

Study concepts, example questions & explanations for GED Math

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Example Questions

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Example Question #1 : Area Of A Circle

A circular swimming pool at an apartment complex has diameter 50 feet. The apartment manager needs to purchase a tarp that will cover this pool completely, but the store will only sell the material in multiples of ten square yards. How many square yards will the manager need to buy?

Use 3.14 for .

Possible Answers:

Correct answer:

Explanation:

The radius of the swimming pool is half the diameter, or 25 feet. 

The area of the swimming pool is  times the square of the radius, or

 square feet, or 

 square yards. 

The manager will need to buy a number of square yards of tarp equal to the next highest multiple of ten, which is 220 square yards.

Example Question #2 : Area Of A Circle

A circular swimming pool at an apartment complex has diameter 30 meters. The apartment manager needs to purchase a tarp that will cover this pool completely, but the store will only sell the material in multiples of ten square meters. How many square yards will the manager need to buy?

Use 3.14 for .

Possible Answers:

Correct answer:

Explanation:

The radius of the swimming pool is half the diameter, or 15 meters. 

The area of the swimming pool is  times the square of the radius, or

 square meters. 

The manager will need to buy a number of square yards of tarp equal to the next highest multiple of ten, which is 710 square meters.

Example Question #3 : Area Of A Circle

Axes_1

Give the circumference of the above circle. Assume each mark on each axis represents one unit.

Possible Answers:

Correct answer:

Explanation:

The diameter of the circle - the distance from one point to the opposite point - is 10 units, so the circumference is this multiplied by , or .

Example Question #4 : Area Of A Circle

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

Possible Answers:

Correct answer:

Explanation:

Be careful on several counts for this question.  First, remember that you need the radius for calculating area.  Therefore, since you know that the diameter is , you can say that the radius is .

Next, be very careful given that there is already a  in your radius.  The formula for the area of a circle is:

For your data, this is:

Example Question #1 : Area Of A Circle

What is the area of the circle with a radius of 25?

Possible Answers:

Correct answer:

Explanation:

Write the formula for the area of a circle.

Substitute the radius into the equation.

Simplify the equation.

The answer is:  

Example Question #6 : Area Of A Circle

Find the area of a circle with a radius of 12.

Possible Answers:

Correct answer:

Explanation:

Write the formula for the area of a circle.

Substitute the radius into the equation.

The answer is:  

Example Question #7 : Area Of A Circle

What is the area of a circle with the diameter of 18?

Possible Answers:

Correct answer:

Explanation:

Write the formula for the area of a circle.

The radius is half the diameter, or 9.

Substitute the value of the radius in to the formula.

The answer is:  

Example Question #2 : Area Of A Circle

Find the area of a circle with a radius of .

Possible Answers:

Correct answer:

Explanation:

Write the formula for the area of a circle.

Substitute the radius into the equation.

Simplify this equation.

The answer is:  

Example Question #9 : Area Of A Circle

Find the area of a circle with a diameter of 22cm.

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 diameter of the circle is 22cm. We also know the diameter is two times the radius. Therefore, the radius is 11cm.

So, we can substitute. We get

Example Question #10 : Area Of A Circle

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

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