University of North Carolina
A Dictionary of Units of Measurement
This site contains an extensive list of various units of measurement known internationally and across several disciplines. Unit symbols are also included.
Saddleback College
Algebra2 Go: Prealgebra
The resource consists of comprehensive learning tools such as class notes, video lectures, and templates through which students can review prealgebra topics.
Khan Academy
Khan Academy: Area of a Circle
Find the area of a circle given its radius, diameter, or circumference. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
Learning Wave Communications
Learning Wave: Geometry, Section 2
Geometry concepts are briefly discussed at this site, including volume of a cylinder, parallelograms, circles, trapezoids, and triangles. Sample problems and applications are included for practice.