Circle Secrets Anchor Chart
Circle Secrets
Anatomy of a Perfect Round
Center
Radius (r)
Diameter (d)
Chord
Circumference (C)
Center
The exact middle point of the circle.
Circumference
The distance all the way around the outside.
Radius (r)
Distance from the center to any point on the edge.
Diameter (d)
Distance across the circle passing through the center.
Chord
A line segment connecting any two points on the circle's edge.
The Golden Rule
Find Diameter
d = 2 × r
Find Radius
r = d ÷ 2
Circle Secrets Worksheet
Circle Secrets Practice
Mastering the Geometry of Circles
Name: __________________________
Date: ___________________________
1
Label the Anatomy
Identify each labeled part of the circle. Use: Center, Radius, Diameter, Chord, Circumference.
A
C
B
D
E
A:
B:
C:
D:
E:
2
The Diameter-Radius Connection
Complete the problems below. Show your work!
1. Radius = 7 cm. Find diameter.
d = ___________
2. Diameter = 24 in. Find radius.
r = ___________
3. Radius = 12.5 m. Find diameter.
d = ___________
4. Diameter = 15 ft. Find radius.
r = ___________
5. Radius = 9.2 cm. Find diameter.
d = ___________
6. Diameter = 16 in. Find radius.
r = ___________
Circle Secret Challenge
Is it possible for a chord to be longer than the diameter of the same circle? Explain why or why not.
Circle Secrets Answer Key
Answer Key
Circle Secrets Practice Pack
TEACHER REFERENCE
Reference Diagram
A
B
C
D
E
1. Label the Anatomy
A: Center
B: Radius
C: Diameter
D: Chord
E: Circumference
2. The Diameter-Radius Connection
Problem 1
7 × 2 = 14 cm
Problem 2
24 ÷ 2 = 12 inches
Problem 3
12.5 × 2 = 25 meters
Problem 4
15 ÷ 2 = 7.5 feet
Problem 5
9.2 × 2 = 18.4 cm
Problem 6
16 ÷ 2 = 8 inches
Circle Secret Challenge
Is it possible for a chord to be longer than the diameter?
No. The diameter is the longest possible chord in any circle because it passes through the center. Any other chord that does not pass through the center will always be shorter than the diameter.
