Reference Topics 3-6

This site presents an interesting logic calculator:

These sites considers logic gates (with links to other logic topics):

This site, Basic Gates and Functions provides a nice discussion of logic circuits: the whole entry

Reference Topics 2-2

This is a web-based instructional module on the algebra of sets.

Union of Sets:

Intersection of Sets:

Venn Diagrams for union and intersection: the whole entry

Reference Topics 1-1

An interactive version of Pascal’s Triangle.

Here is another site on Pascal’s triangle:

This site give a nice introduction to problem-solving.
A site which lists other sites on mathematical puzzles: the whole entry