What I like about these apps, beyond the fact that they are free, are that they support understanding math visually and correlate with national math standards and Bridges.
If your child is still working on adding and subtracting fluently, here a link to the app on finding sums. http://itunes.apple.com/us/app/id353582286?mt=8
If your child has a hard time with reading clocks, or could just use some practice, here is a link to the app on reading clocks: http://itunes.apple.com/us/app/mathtappers-clockmaster-math/id336932114?mt=8
If your child is working on multiplication and division, here is the app that supports understanding both concepts and gaining fluency. http://itunes.apple.com/us/app/mathtappers-multiples-math/id371520443?mt=8
