Khan Academy
Khan Academy: Practice: Area of a Circle
A practice quiz on calculating the area of a circle. Includes hints.
Varsity Tutors
Varsity Tutors: Hotmath: Algebra Review: Circumference
Find a quick, concise explanation of circumference. The formula for finding the circumference of a circle is explained.
Math Is Fun
Math Is Fun: Definition of Circumference
Definition of circumference. Click the "here's more" link to learn more about a circle; its radius and diameter, area, lines, slices and common sectors.
Calculator Soup
Calculator Soup: Circle Calculator
Use this circle calculator to find the area, circumference, radius, or diameter of a circle. Given any one variable A, C, r or d of a circle you can calculate the other three unknowns.
Mocomi & Anibrain Digital Technologies
Mocomi: What Is Circle?
Discusses the radius, diameter, circumference, and area of a circle.
Wolfram Research
Wolfram Math World: Circle
This site from Mathworld provides a wealth of information about circles is presented. The information ranges from the basics--radius, circumference, etc.--to advanced concepts--equations in polar and pedal coordinates, etc.
Wolfram Research
Wolfram Math World: Circumference
This site provides the formula for circumference. Links are provided.
Homeschool Math
Homeschool Math: Circles
Lesson presents definitions of terms associated with circles and helps students learn to use a compass to draw circles and simple circle designs.
Ducksters
Ducksters: Kids Math: Circle Geometry
Circle Geometry math for kids contains information for students to learn about terms radius, diameter, circumference, chord, and pi.
Other
Circles/circumference Interactive Learning Sites for Education
Includes record sheets and interactive media exploring circles and circumference from general parts of the circle to the relationship of the circle parts.
Oswego City School District
Regents Exam Prep Center: Area of Polygons and Circles
A lesson focusing on the area of polygons and the circumference of circles. Engaging, interactive practice worksheet, lesson plan, and related classroom activity complete this lesson.
CK-12 Foundation
Ck 12: Geometry: Inscribed Angles in Circles
[Free Registration/Login may be required to access all resource tools.] This concept teaches students properties of inscribed angles and how to apply them.
ClassFlow
Class Flow: Area of a Circle
[Free Registration/Login Required] This flipchart reviews basic geometric forms in nature and real objects. Students are then given opportunities to find the area of circle and parts of a circle, given the radius and/or diameter of the...
CK-12 Foundation
Ck 12: Circumference Medium Circle and Circle Units
[Free Registration/Login Required] Students will determine the circumference of circles by moving smaller circle units. Click challenge me to answer practice questions and click learn more to watch a video.
CK-12 Foundation
Ck 12: Circumference: Big Circle & Circle Units
[Free Registration/Login Required] Sudents use circle units to explore circumference in a big circle. Click challenge me to answer practice questions and click learn more to watch a video.
CK-12 Foundation
Ck 12: Circumference vs. Radius
[Free Registration/Login Required] Students use the points on a circle to explore circumference and radius. Click challenge me to answer practice questions and click learn more to watch a video.
CK-12 Foundation
Ck 12: Circumference: Ancient Stonehenge Math Mysteries
[Free Registration/Login Required] Students change the length of a radius to explore the circumference of a circle. Click challenge me to answer practice questions and click learn more to watch a video.
McGraw Hill
Glencoe Mathematics: Online Study Tools: Self Check Quiz on Circles
Students show comprehension of advanced mathematics skills in Geometry. The questions check understanding on circles. Topics include diameters, angles, and finding the circumference.
Other
Visnos: Explore Pi
This interactive demonstration shows firstly how pi relates to the circumference of a circle. This is achieved using a regular polygon approximation, the closed polygon is opened to reveal this magical number. The area of a circle is...
Government of Alberta
Learn Alberta: Exploring the Diameter and Circumference
This multimedia site offers a beginner's guide to understanding the relationship between the diameter and circumference of a circle. This Learn Alberta site offers a video [1:44], interactive exercises and printable extended exercises.
Ministry of Education and Universities of the Region of Murcia (Spain)
Ministerio De Educacion Y Ciencia: La Circunferencia
In Spanish. In this interactive activity you will get a clear understanding of the definition the circumference of a circle and have fun while learning the relationship between equations and figures.
Texas Instruments
Texas Instruments: Math Today Coming Clean About Showering Time
In this activity using the USA TODAY Snapshot, "Coming clean about showering time," students will find the measures of central angles and arcs of a circle. They will use circumference, radius, concentric circles and degrees in a circle...