CK-12 Foundation
CK-12 Middle School Math Concepts - Grade 6
Twelve chapters cover a multitude of math concepts found in the Common Core standards for sixth grade. Each title provides a brief explanation of what you will find inside the chapter—concepts from which you can click on and learn more...
Math Planet
Math Planet: Geometry: Measure Line Segments
Explores how to measure the length of a line segment through examples and a video lesson. [0:40]
Mathigon
Mathigon: Geometry: Circle and Pi: Degrees and Radians
Rather than dividing a circle into some number of segments (like 360 degrees), mathematicians often prefer to measure angles using the circumference of a unit circle - a circle with radius 1. This way of measuring angles is called...