1. Finding the area of circles

2. Radius vs. Diameter
A RADIUS is the distance from the center of a circle to any point on the outside!
A DIAMETER is the distance across the center of a circle, from one side to the other!
REMEMBER: If a circle is cut in HALF, it will DIE…this means a line cutting a circle in HALF is the DIAMETER!!!

3. Is the FRACTION form of PI….just in case you need it!!! : D
Whats that sign???
A =  r2
To find the AREA of a circle we have to square the radius and then times it by PI.
A = 3.14 ● r ● r 22
This is a GREAT way to write the formula so that you can remember it easily.ut But you need to know what r2 means when you see the formula normally! 7
Is the FRACTION form of PI….just in case you need it!!! : D

4. Lets try one!!!
Plug the numbers in 1st !
A =  r2
A = x 2 x 2
2 ft.
Do the square numbers
A = x 4
3.14
x 4
12.56
A = ft2

5. What’s different here???
A =  r2
Change the Diameter to a Radius 1st !!!
A = x 8 x 8
16 in
Do the square numbers
A = x 64
3.14
x 64
1256
+1884x
200.96
A = in2

6. What if you have a semi-circle???
A = ½  r2
Since only half the circle is used, use HALF of PI
A = 1.57 x 4 x 4
4 m
A = 1.57x 16
1.57
x 16
942
+157x
25.12
A = in2