Vocab
Where is the center of the circle? (draw it)
In the middle! (should have a dot in the middle of a circle)
What are we measuring when someone says "find the circumference?"
The distance or perimeter around the circle.
Find the circumference of a circle with a radius of 2.
C=2π r
12.56
Find the area of a circle with a radius of 3
A=πr²
28.26
how many radii are in a circle?
Infinite! They can be anywhere on the circle, not in one particular spot.
What is a radius?
Any line on a circle that starts at the center and goes to the edge.
What does area mean?
The amount of space inside a shape
Find the circumference when the radius is 12
C=2πr
75.36
Find the area of a circle with a radius of 5
A=πr²
78.50
If I am given the following information, what am I finding? Cindy wants to decorate a circular mirror by placing beads around the edge of it. She knows the diameter of the mirror is 5. How much beading will she need to decorate the edge?
You are finding circumference.
C=πd
What is a diameter?
Any line that goes all through the center of the circle and goes edge to edge.
What does it mean to work backwards with circumference?
It means they already gave you the circumference and you have to figure out the radius. You have to undo the operations by dividing.
Find the radius when given a circumference of 18.84
C=2πr
3
Find the area of a circle with a radius of 10
A=πr²
314
When working backwards with circumference, you must... (if it gave you circumference and you need to find the radius)
Divide the circumference by pi and 2. (3.14 x 2 then divide)
What does substitution mean?
Replacing letters (variables) with numbers
Tell me the steps to find the area of the following shape...
Find the area of the triangle.
Find the area of the rectangle.
Add them together.
Find the diameter when given a circumference for a circle of 21.98
C=πd
7
Find the area of a circle with a diameter of 8
A=πr²
50.24
If I am given the following information, what am I finding?
Mrs. Walker is trying to decide how much paint to buy for a project. She is painting 2 different types of circle signs.
One sign has a radius of 5, and the other sign has a radius of 2. How much total paint does Mrs. Walker need to buy?
Area. find the area of both shapes and add them together.
What is the definition of pi? (not just 3.14)
The ratio between a circle circumference and diameter. When dividen you should get approx. 3.14.
A complicated shape that can be broken down into smaller, simpler shapes
Find the radius when given a circumference for a circle of 12.56
C=2πr
r = 2
The area of a circle is 153.86. What is the radius?
A=πr²
7
The circumference for a circle is A centimeters. The radius of that circle is 10. Write an expression to represent the value of pi (π)
C
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20
(C over D)