For this week in math class, I learned about circles and regular polygons. But, I will only be talking about circles today. Most of this should be a review. So, the radius is the line that goes from the center to the circumference of the circle. The diameter is the line that goes across the center from one side of the circumference to the other side. Remember, the radius is always half of the diameter. We have two formulas, one to find the circumference, and one to find the area. The formula to find the circumference is C=πd or C=2πr. In words, the circumference is either equal to pi multiplied by the diameter or the radius multiplied by two multiplied by pi. So, all you need to know is the diameter to solve the for the circumference. To find the area, the formula is A=πr^2. In words, that means that the area is equal to pi times the radius squared. Here is an example.

Find the area of the circle when the diameter is equal to 6 meters. So, we will use the formula A=πr^2. To get the radius, divide the diameter by 2, so the radius is 3. You will then square that number, which is equal to 9. You will multiply 9 by π. You can use 3.14 as pi to make it a little simpler. Once you multiply 9 and π, you get 28.26, which is the area of the circle. I hope you learned something.