# High School Math : How to find the area of a circle in pre-algebra

## Example Questions

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

What is the area of circle with a radius of ?

Explanation:

To find the area of a circle you must plug the radius into  in the following equation

In this case the radius is  so we plug it into  to get

We then multiply it by  to get our answer .

### Example Question #2 : How To Find The Area Of A Circle In Pre Algebra

What is the area of a circle with radius of ?

Explanation:

The formula for the area of a circle is .

Plug in our given values:

### Example Question #3 : How To Find The Area Of A Circle In Pre Algebra

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

Explanation:

The formula for the area of a circle is .

Plug in the information given and solve:

Remember, a number squared is just the same as that number times itself:

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

If the area of a circle is , what is the radius of the circle?

Explanation:

The formula for the area of a circle is .

Plug in the information given and solve:

Notice that the 's cancel out:

Take the square root of both sides:

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

If the diameter of a circle is , what is the area of that circle?

Explanation:

The area of a circle is , but the problem gives us the diameter and not the radius.

The diameter is twice the radius, so . We can plug in our given values to find the radius:

Now we can plug this value into our equation for area:

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

If the area of a circle is , what is the length of the radius?

Explanation:

The formula for the area of a circle is . Plug in our given information to solve:

The 's cancel out, leaving us with:

Take the square root of both sides:

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

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

Explanation:

The formula for area of a circle is .

Plug in our given information:

### Example Question #2 : How To Find The Area Of A Circle In Pre Algebra

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

Explanation:

The formula for area of a circle is .

Plug in our given information:

### Example Question #9 : How To Find The Area Of A Circle In Pre Algebra

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

Explanation:

The formula for area of a circle is . However, the problem gives us the diameter instead of the radius. The diameter is twice the length of the radius:

We can plug that back into our area equation:

### Example Question #10 : How To Find The Area Of A Circle In Pre Algebra

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