Finding radius, diameter, circumference and area of circles (HD) August 8, 2014 by Hope Ballou This video teaches clearly about circles, what radius and diameter is?, how circumference is calculated?, what is π (pi) after all?, why pi r squared is used…

Circles: Radius, Diameter and Circumference January 19, 2013 by Edward Ramos Learn more: www.khanacademy.org Understanding the relationship between the radius diameter and circumference of a circle.