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

## Example Questions

### Example Question #1 : Area Of A Circle

What is the area of a circle that has a diameter of inches?

Explanation:

The formula for finding the area of a circle is . In this formula, represents the radius of the circle.  Since the question only gives us the measurement of the diameter of the circle, we must calculate the radius.  In order to do this, we divide the diameter by .

Now we use for in our equation.

### Example Question #1 : Know And Use The Formulas For The Area And Circumference Of A Circle: Ccss.Math.Content.7.G.B.4

What is the area of a circle with a diameter equal to 6?

Explanation:

Then, solve for area:

### Example Question #1 : Radius

The diameter of a circle is . Give the area of the circle.

Explanation:

The area of a circle can be calculated using the formula:

,

where is the diameter of the circle, and is approximately .

### Example Question #4 : Area Of A Circle

The diameter of a circle is . Give the area of the circle in terms of .

Explanation:

The area of a circle can be calculated using the formula:

,

where   is the diameter of the circle and is approximately .

### Example Question #5 : Area Of A Circle

The radius of a circle is  . Give the area of the circle.

Explanation:

The area of a circle can be calculated as , where   is the radius of the circle, and is approximately .

### Example Question #41 : Circles

The circumference of a circle is inches. Find the area of the circle.

Let .

Explanation:

First we need to find the radius of the circle. The circumference of a circle is , where is the radius of the circle.

The area of a circle is where   is the radius of the circle.

### Example Question #1 : Area Of A Circle

The radius of a circle is 4 cm, what is the area?

Explanation:

The area of a circle is found by: , where r is the radius.

.

The area of the circle is .

### Example Question #8 : Area Of A Circle

The radius, , of the circle below is 18 units. What is the area of the circle?

square units

square units

square units

Cannot be determined

square units

square units

Explanation:

The formula for the area, , of a circle with radius  is:

We can fill in

You could do the arithmetic to get an area of about 1,017.876 square units, but it is ok and more precise to leave it as shown.

### Example Question #1 : How To Find The Area Of A Circle

Give the area of a circle with diameter 13.

Explanation:

Half of the diameter 13 is the radius . Use the area formula:

### Example Question #1 : Area Of A Circle

How many times greater is the area of a circle with a radius of 4in., compared to a circle with a radius of 2in.?