Circles operate with a special set of rule that are slightly different from the other geometric shapes we will cover in 7th grade. One of the most important concepts when working with circles is the knowledge of a special number specific to cricles. This number is called:
Pi or π
Pi = 3.14 or 22/7
Pi or π
Pi = 3.14 or 22/7
Diameter vs. Radius
![Picture](/uploads/2/0/1/1/20114429/4744085.jpg?270)
There are many measurements associated with circles, but the two most important in 7th grade math will be the diameter and the radius.
The radius of a circle is a measurement of the distance between the center of the circle and a point on the outside of the circle. The radius can extend from the center in any direction
The diameter of a circle is the measurement of the distance it takes to cross the entire circle, apssing through the center. Because of this, the measure of the diameter is always twice the measure of the radius.
2 r = d or d / 2 = r
The radius of a circle is a measurement of the distance between the center of the circle and a point on the outside of the circle. The radius can extend from the center in any direction
The diameter of a circle is the measurement of the distance it takes to cross the entire circle, apssing through the center. Because of this, the measure of the diameter is always twice the measure of the radius.
2 r = d or d / 2 = r
Circumference of a Circle
![Picture](/uploads/2/0/1/1/20114429/1961517.jpg?200)
The circumference of a circle is the measurement of the distance around the outside of the circle.
The formula for the circumference of a circle is Circumference = Pi x Diameter or C = π d
So if I have a circle with a diameter of 12cm :
C = π (12)
C = 3.14 x 13
C = 40.82 cm
This means that the distance around the outside of the circle or the perimeter of the circle is about 41 cm.
The formula for the circumference of a circle is Circumference = Pi x Diameter or C = π d
So if I have a circle with a diameter of 12cm :
C = π (12)
C = 3.14 x 13
C = 40.82 cm
This means that the distance around the outside of the circle or the perimeter of the circle is about 41 cm.
Area of a Circle
![Picture](/uploads/2/0/1/1/20114429/7132990.jpg?183)
The area of a circle is a measure of the surface contained within that circle. Area is always measured in square units.
The formula for area of a circle is: Area = Pi x Radius x Radius or A = π (r x r)
So if i have a circle with a radius of 2 in :
A = π (2 x 2)
A = 3.14 (2 x 2)
A = 3.14 (4)
A = 12.56 square inches
The formula for area of a circle is: Area = Pi x Radius x Radius or A = π (r x r)
So if i have a circle with a radius of 2 in :
A = π (2 x 2)
A = 3.14 (2 x 2)
A = 3.14 (4)
A = 12.56 square inches