The document is a study guide for a math quiz on circles that covers circumference and area. It defines key circle terms like diameter, radius, and chord. It provides the formulas for calculating circumference (C=2πR) and area (A=πR^2) of a circle and explains that if a question gives the diameter, the radius needs to be halved to use the formulas correctly. Examples are given for finding the circumference and area of circles using different radii.

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