Purple Math
Purplemath: Practical Algebra Lessons
Pre-algebra and algebra lessons, from negative numbers through pre-calculus. Grouped by level of study. Lessons are practical in nature informal in tone, and contain many worked examples and warnings about problem areas and probable...
Math Planet
Math Planet: Combinations and Permutations
Gain an understanding of combinations and permutations by viewing an example and a video lesson. [1:15]
National Council of Teachers of Mathematics
Nctm: Standards for School Mathematics
This standards-based NCTM website offers resources for teachers of mathematics for all grade levels, including interactive math tools, lesson plans, online resources, and the like.
Math Planet
Math Planet: Calculating the Outcome
Gain an understanding of how to calculate the outcome using a tree-diagram by viewing an example and a video lesson.