Radius or Diameter?
A line that goes from the center of the circle to any point on the edge.
What is Radius
You are told the radius is 4 cm. Which formula would you use
What is C = 2πr
Draw a circle:
Line from center to edge.
What is Radius — C = 2πr?
The diameter is always smaller than the radius
False
What part of a circle touches the circumference?
Radius
A line that passes all the way through the circle and through its center.
What is Diameter
The diameter of a circle is 10 cm. Which formula would you use?
What is C = πd?
Draw a circle:
Line passing through entire circle.
What is Diameter — C = πd?
You can find circumference if you only know the radius.
True
Which formula uses the diameter?
C = πd
This line is half as long as the diameter.
What is radius
You are told the distance across the circle is 8 cm. Which formula would you use?
What is C = πd?
Draw a circle:
Two radius drawn from the same center.
Together make a diameter — C = πd?
The formula C = πd is the same as C = 2πr.
True
A circle’s radius is 5 cm. What is its diameter?
10 cm
This line is twice as long as the radius
What is diameter
You only know the distance from the center to the edge is 6 cm. Which formula would you use?
what is C = 2πr?
Draw a circle:
Label shows r = 7 cm.
Radius — C = 2πr?
The radius goes across the entire circle.
False
The symbol π (pi) is approximately equal to what?
3.14
The circle’s measurement that helps find the circumference using the formula C = 2πr.
What is radius
You are given the diameter but accidentally use the radius formula. What must you do first?
what is Divide the diameter by 2 to get the radius?
Draw a circle:
Label shows d = 12 cm.
Diameter — C = πd?
If you double the radius, you get the diameter.
True
You’re given a diameter but want to use the formula
C = 2πr. What must you find first?
The radius (divide diameter by 2)