Formulas
Parts of a Circle
Circumference
Area
Composite Shapes & Half Circles
100
What is the ratio for Pi, when given the diameter and circumference?
Pi = Circumference/ Diameter
100
The distance around the circle is called what?
Circumference
100
A circle has a diameter of 2 inches. Solve for the circumference.
C = (Pi)(Diameter)
C = (3.14)(2)
C= 6.28 inches
100
What does it mean when I "square" a number of I see an exponent of 2?
Ex: 22
It means you multiply the number by itself two times.
Ex: 22 is the same as (2)(2)
100
What is a composite shape?
A shape that is made up of 2 or more shapes
200
What is one of the formulas for circumference when given the diameter?
C = (Pi)(Diameter)
200
What is the space inside a shape called? Its also the number of square units needed to cover a surface?
Area
200
A circle has a radius of 5.5 centimeters. What is the circumference?
C = (2)(Pi)(Radius)
C = (2)(3.14)(5.5)
C = (3.14)(11)
C = 34.54 Centimeters
200
If you are given the diameter and are told to solve the area of a circle? What should you do first?
Divide the diameter by 2 to get the radius
You need the radius to solve for the area of a circle
Area = (Pi)(Radius2)
Area = (Pi)(Radius)(Radius)
200
What are my steps to find area of a composite shape?
Step 1:
Split up the composite shape into 2 or more shapes. (Get a few shapes as you possible can)
Step 2:
Find the missing lengths of the unknown sides
Step 3:
Solve for the area of each shape
Step 4:
Add up all the area of each of the shapes
300
What is the formula for circumference when given the radius?
C = (2)(Pi)(Radius)
300
A line that goes from the center of the circle to the edge.
Also a line that goes halfway through the circle?
Radius
300
A circle has a diameter of 25 yards. What is the circumference?
C = (Pi)(Diameter)
C = (3.14)(25)
C = 78.5 yards
300
A circle has a radius of 5 inches. What is the area?
A = (Pi)(Radius2)
A = (3.14)(5)(5)
A= (3.14)(25)
A = 78.5 in2
300
What do I do if I have to find the area of a half circle?
Double Points
What do I do if I have to find the area of a quarter circle?
For a half circle, you need to find the area like its a WHOLE circle, then divide the area by 2 to get the area of a half circle
Double Points
For a quarter circle, you need to find the area like its a WHOLE circle, then divide the area by 4 to get the area of a quarter circle
400
What do I need to find for the Area of a circle?
Radius
400
A line that goes all the way through the circle and through the center?
Diameter
400
A circle has a radius of 50 inches. What is the circumference?
C = (2)(3.14)(50)
C = (3.14)(100)
C = 314 inches
400
A circle has a radius of 25 meters. What is the area?
A = (Pi)(Radius2)
A = (3.14)(25)(25)
A= (3.14)(625)
A = 1962.5 m2
400
Find the area of this composite shape.
Area of Rectangle
A = (L)(W)
A = (12)(16)
A = 192 ft2
Area of the Half Circle
Diameter is 12, so the radius is 6
A = (3.14)(Radius2)
A = (3.14)(62)
A = (3.14)(36)
A = (113.04)/2
A = 56.52 ft2
Area of Rectangle + Area of Half Circle
192 + 56.52 = 248.52 ft2
Total Area = 248.52 ft2
500
What is the formula for area of a circle?
A = (Pi)(Radius)(Radius)
500
A closed shape with no sides and no angles is called what?
A Circle
500
A circle has a diameter of 250 meters. What is the circumference
C = (Pi)(Diameter)
C = (3.14)(250)
C = 785 meters
500
A circle has a diameter of 12 feet. What is the area?
Diameter to Radius --> Divide by 2
12/2 = 6 So the radius is 6
A = (Pi)(Radius)(Radius)
A = (3.14)(6)(6)
A = (3.14)(36)
A = 113.04 ft2
500
Find the area of the composite shape
Area of Triangle
A = (Base)(Height)/2
A = (15)(13)/2
A = 195/2
A = 97.5 cm2
Area of the Half Circle
Diameter is 12, so the radius is 6
A = (3.14)(Radius2)
A = (3.14)(7.52)
A = (3.14)(56.25)
A = (176.63)/2
A = 88.31cm2
Total Area
97.5 + 88.31 = 185.81