Lawrence Hall of Science
The Math Page: Skill in Arithmetic: The Meaning of Multiplication: Mental Calculation
If you are looking for a website that explains and defines the basics of mental multiplication with helpful hints then you have arrived at an excellent resource. There are even practice problems at the very end of the lesson.
Khan Academy
Khan Academy: Meaning of Multiplication
Practice representing multiplication as equal groups, repeated addition, or arrays. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints. Video content is available for...