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Khan Academy
Khan Academy: Area and Circumference of Circles Challenge
Practice interesting area and circumference problems. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
Khan Academy
Khan Academy: Circumference of a Circle
Find the circumference of a circle when given either the radius or diameter.Find the radius or diameter of a circle when given the circumference.Students receive immediate feedback and have the opportunity to try questions repeatedly,...
National Council of Teachers of Mathematics
The Math Forum: Elementary Geometry Circles
The Math Forum offers an archive of question and answer sessions on circles and how they relate to geometry.
Texas A&M University
Wtamu Virtual Math Lab: Beginning Algebra: Formulas
This tutorial will show you how using formulas can help you solve problems. Include formulas for various geometric shapes and steps showing how to use them.
Cool Math
Coolmath: Precalculus Basic Formulas to Know
This CoolMath resource provides an introduction to some Precalculus formulas.