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Khan Academy
Khan Academy: Praxis Core Math: Circles Lesson
A basic review of circles and how to calculate the circumference, radius, diameter, and area. Includes practice questions.
Khan Academy
Khan Academy: Practice: Area of a Circle
A practice quiz on calculating the area of a circle. Includes hints.
National Council of Teachers of Mathematics
The Math Forum: Pi Day
Need some ideas for Pi Day on March 14th? You can get some great resources at this location. There are all kinds of links available.
Homeschool Math
Homeschool Math: Circles
Lesson presents definitions of terms associated with circles and helps learners learn to use a compass to draw circles and simple circle designs.