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Saskatoon Public Schools: Mental Math Strategies
Strategies for basic addition and multiplication are explained here and there are several practice worksheets that can be downloaded.
Teachnology
Teachnology: Addition and Subtraction Teaching Theme
Addition and Subtraction Math Theme provides an excellent collection of free sample worksheets, teacher resources, lesson plans and interactive media to support addition and subtraction skills.
Math Playground
Math Playground: Tug Boat Addition
Practice your addition facts for numbers 1-20 in this tug boat game.