Wolfram Demonstrations Projecthttp://demonstrations.wolfram.com/An Open Resource of Interactive Mathematica VisualizationsCopyright 2009 Wolfram Demonstrations Project & ContributorsMixed and Improper Fractionshttp://demonstrations.wolfram.com/MixedAndImproperFractions/]]>http://demonstrations.wolfram.com/MixedAndImproperFractions/Addition of Fractionshttp://demonstrations.wolfram.com/AdditionOfFractions/]]>http://demonstrations.wolfram.com/AdditionOfFractions/Using Common Denominators to Add Fractionshttp://demonstrations.wolfram.com/UsingCommonDenominatorsToAddFractions/]]>http://demonstrations.wolfram.com/UsingCommonDenominatorsToAddFractions/