Identify parts of a circle
What is a radius?
The distance from the center of the circle to the outer edge.
How are the radius and diameter of a circle related?
The radius is half of the diameter.
OR
The diameter is double the radius.
Part 1: What is circumference?
Part 2: Is the relationship between diameter and circumference proportional or not?
Part 1: The measurement of the length of the outer edge of a circle.
Part 2: It is proportional.
Where can you find the area of a circle?
Inside the circle
What is a diameter?
The distance across the circle that goes through the middle.
If the radius of a circle is 7.5, what is the diameter?
7.5 x 2 = 15
What are the equations for circumference?
C = pi x diameter
C = pi x radius x 2
What is the formula for area of a circle?
Area = 3.14 x r2
What is the circumference of a circle?
The length measured around the outer edge of a circle
What is the diameter of a circle with a radius of 90cm?
90cm x 2 = 180cm
What is the estimated circumference of a circle if it has a diameter of 5m?
C = 3 x 5m = 15m
Estimated Answer: Just over 15m.
What is the area of a circle with a radius of 5in?
A = 3 x 5 x 5 = 75in
Where can you find the area of a circle?
Inside the circle.
If the diameter of a circle is 225, what is the radius?
225/2 = 112.5
If you are given a radius of 7cm, what is the circumference?
C = 3.14 x 7cm x 2 = 43.96cm
What is the area of a circle with a diameter of 14?
A = 3.14 x 7 x 7 = 153.86
Draw a diagram of a tire, and label the radius, diameter, circumference and area.
Teacher check.
If the radius of the circle is 194.689, what is the diameter? Round to the nearest hundredth.
194.689 x 2 = 389.38
What is the diameter of a circle that has a circumference of 221mm? Round to the NEAREST HUNDREDTH.
C = 3.14 x diameter
221mm = 3.14 x diameter
221mm/3.14 = diameter
diameter = 70.38mm
What is the area of a circle with a radius of 123.45? ROUND TO THE NEAREST HUNDREDTH.
A = 3.14 x 123.45 x 123.45 = 47853.29