How to find Area of a Circle in 5 Easy Steps

What is the Area of a Circle formula?

Finding Area of a Circle Practice Problems Quiz

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Watch our free video on How to find Area of a Circle. This video shows how to solve problems that are on our free finding the Area of a Circle worksheet that you can get by submitting your email above.

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Video Transcript:

This video is about how to find the area of a circle. You can get the 7th grade area of a circle worksheet used in this video for free by clicking on the link in the description below.

Finding area of circle of a circle you have to use the area of a circle formula. This circle area formula says that the area of a circle is equal to pi times the radius squared. The radius is from the middle point of the circle to the outer edge. It does not matter which way you draw the radius because the distance from the center of the circle to the outer edge will be equal no matter where you draw it.

Now let’s say you’re told that the radius is 4 inches. You will take this information and you will substitute it into the formula where radius is supposed to go. So your formula will change from pi r squared into pi times the radius, which in this case is 4, squared and then you simplify 4 times 4. 4 squared which is 16 and then you do pi times 16, which is equal to 50.27 inches squared.

You may also be given a problem in which instead of giving you the radius they give you the whole diameter of the circle. Now the diameter of the circle is the distance all the way across the middle of the circle. Instead of just being from the middle to the outside edge, it’s from one edge of the circle directly across to the other edge of the circle that goes through the middle. In this case you have to remember that the diameter is equal to twice the size of the radius. In other words, you have to take the diameter and divide it by 2 in order to get the radius. If they gave you a diameter of let’s say 12 feet you have to take the diameter, in this case is 12 feet, and divide it by 2 in order to get the radius. So if the diameter was 12 feet then the radius would be equal to 6 feet. Once you know the radius, in this case is 6, then you can use your formula which is area is equal to pi times the radius squared. Again we know the radius is 6 this time, so we take 6 substitute it in for r so you do pi times 6 squared. Then you do 6 squared first, according to the order of operations, which is 36 and then you do pi times 36 which is 113.1 feet squared.

Let’s try a couple practice problems on our area of a circle worksheet. Problem number one to practice how to find area of circle gives us 5 inches for the radius. Now we know the circle formula area equals pi times the radius squared. In this case we know the radius is 5 inches and I know it’s referring to the radius because it’s only half of the circle. If it went all the way across that would be the diameter, but in this case because it’s only half, that’s going to be the radius. We know the radius is 5 inches so we’re going to say radius equals 5, and now we can substitute 5 in for where the radius used to be. So we’re going to take our formula which is area equals pi times the radius, which in this case is 5 squared, then order of operations says we do 5 squared so we do pi times 5 squared which is 25. And then we do pi times 25 which gives us 78.55 inches squared and that’s going to be our solution.

Moving on to the fourth problem on our area of a circle worksheet it gives us 22 centimeters for the diameter. So this time we are figuring out area of a circle with diameter. I know its diameter because the line goes all the way across the circle, so because it goes all the way across that’s referring to the diameter. We know this time that we’re going to be using or we’re going to be starting with the diameter. In this case the diameter is equal to 22 centimeters. Now if you remember diameter is twice the radius which means in order to get the radius you have to take the diameter and divide it by 2. S the diameter, which is 22 divided by 2 is 11, so 22 divided by 2 is 11. We know the radius now is 11 and we can take the radius which is 11 and now we can substitute it in for r in our area formula. We have area equals pi times the radius which in this case is 11 squared. Then you’re going to square 11 so 11 times 11 is 121 and then you’re going to do pi times 121 and then pi times 121 is 380.13 centimeters squared. If you’re finding area of a circle with diameter you just have the extra step of dividing diameter by two to get the radius.