Wolfram Demonstrations Projecthttp://demonstrations.wolfram.com/An Open Resource of Interactive Mathematica VisualizationsCopyright 2009 Wolfram Demonstrations Project & ContributorsLearning Place Value by Counting Squareshttp://demonstrations.wolfram.com/LearningPlaceValueByCountingSquares/]]>http://demonstrations.wolfram.com/LearningPlaceValueByCountingSquares/