1. Name __________________________________________ Date ____________
Polizzi/Denman Math – 6
Study Guide
Circles
Topics on Quiz:
1. Circumference of a circle
2. Area of a circle
Diameter: Line segment from arc to arc through the midpoint of the circle. Diameter is twice
the radius.
Radius: ½ the diameter of a circle, it’s a line segment from midpoint on the circle to the arc.
Chord: Line segment from arc to arc but not through the midpoint of the circle.
Circumference of a circle
• Circumference: the distance around a circle (outside).
C=2π R
C=2πR
= 2 (π) (2)
=4π
• If the circle shows the diameter, you need to take half to find the radius.
C=2πR
= 2 (π) (1.5)
=3π

2. Area of a circle
• Area: the number of square units inside that circle.
A = π R²
A = π R²
= π (3) 2
=9π
• If the circle shows the diameter, you need to cut it in half to find the
radius.
A = π R²
= π (4) 2
= 16 π