Reform Education Now
Math demos
This page contains a number of links to math demos. Some of the demos have hints or graphs for students to help with the problems. While not currently built in these hints could be turned on and off. While learning it would help a child to see how things work. However for testing such hints would be in many cases excessive.

You will need a browser that supports the HTML 5 canvas system. If you are using Internet Explorer you will need 9 or later. You may need to check the compatibility option in the url bar.
Chrome and Firefox both work for these demos.

Add 1 by 1
Add 1 by 2
Add 2 by 2
Add 3 by 3
Multiply 1 by 1
Multiply 1 by 2
Multiply 1 by 3
Multiply 2 by 3
Multiply 3 by 3
subtract 1 by 1
Solve rectangle area and perimeter
Solve triangle area
Solve triangle hypotenuse