Common Core: 7th Grade Math : Area of a circle

Study concepts, example questions & explanations for Common Core: 7th Grade Math

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Example Questions

Example Question #11 : Area Of A Circle

Find the area of a circle that has a radius of .

Possible Answers:

Correct answer:

Explanation:

Use the following formula to find the area of a circle:

For the circle in question, plug in the given radius to find the area.

In our particular case the radius is .

When squarring a fraction we need to square both the numerator and the denominator.

Example Question #12 : Area Of A Circle

Find the area of a circle that has a radius of .

Possible Answers:

Correct answer:

Explanation:

Use the following formula to find the area of a circle:

For the circle in question, plug in the given radius to find the area.

In this problem the known radius is 

Now plug the radius into the area equation.

Therefore we get,

Recall that when a square root is squared you are left with the number under the square root sign. This happens because when you square a number you are multiplying it by itself. In our case this is,

.

From here we can use the property of multiplication and radicals to rewrite our expression as follows,

and when there are two numbers that are the same under a square root sign you bring out one and the other number and square root sign go away.

 

Example Question #11 : How To Find The Area Of A Circle

What is the area of a circle with a diameter of , rounded to the nearest whole number?

Possible Answers:

\dpi{100} 81

\dpi{100} 64

\dpi{100} 255

\dpi{100} 254

Correct answer:

\dpi{100} 64

Explanation:

The formula for the area of a circle is

\dpi{100} \pi r^{2}

Find the radius by dividing 9 by 2:

\dpi{100} \frac{9}{2}=4.5

So the formula for area would now be:

\dpi{100} \pi r^{2}=\pi (4.5)^{2}=20.25\pi \approx 63.6= 64

Example Question #13 : Area Of A Circle

If this circle has a diameter of 12 inches, what is its area?

Circle_12d

Possible Answers:

None of the other answers are correct.

Correct answer:

Explanation:

To find the area, we need to determine the radius of the circle first.  

The radius is calculated as , where D is the diameter.

Given that the diameter is 12 inches, the radius is , or .

Next, we know that the formula for the area of the circle is .

Using the radius we just found, we can find the area:

Example Question #13 : Area Of A Circle

What is the area of the circle provided? 

1

Possible Answers:

Correct answer:

Explanation:

In order to solve this problem, we need to recall the formula for the area of a circle: 

The circle in this question provides us with the radius, so we can use the formula to solve:

Solve:

Example Question #14 : Area Of A Circle

What is the area of the circle provided? 


2

Possible Answers:

Correct answer:

Explanation:

In order to solve this problem, we need to recall the formula for the area of a circle: 

The circle in this question provides us with the radius, so we can use the formula to solve:

Solve:

Example Question #15 : Area Of A Circle

What is the area of the circle provided? 


3

Possible Answers:

Correct answer:

Explanation:

In order to solve this problem, we need to recall the formula for the area of a circle: 

The circle in this question provides us with the radius, so we can use the formula to solve:

Solve:

Example Question #16 : Area Of A Circle

What is the area of the circle provided? 

4

Possible Answers:

Correct answer:

Explanation:

In order to solve this problem, we need to recall the formula for the area of a circle: 

The circle in this question provides us with the radius, so we can use the formula to solve:

Solve:

Example Question #17 : Area Of A Circle

What is the area of the circle provided? 


5

Possible Answers:

Correct answer:

Explanation:

In order to solve this problem, we need to recall the formula for the area of a circle: 

The circle in this question provides us with the radius, so we can use the formula to solve:

Solve:

Example Question #14 : Area Of A Circle

What is the area of the circle provided? 


6

Possible Answers:

Correct answer:

Explanation:

In order to solve this problem, we need to recall the formula for the area of a circle: 

The circle in this question provides us with the radius, so we can use the formula to solve:

Solve:

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