How I Use It
Number Rack by Math Learning Center is a free app provided to be used in conjunction with their curriculum, Bridges 2. However, it's a great app for use with any math program with instruction using a rekenrek or abacus. Through experiences using Number Rack with second grade students, I found that students could use this app instead of or in addition to a standard rekenrek or abacus. One especially nice feature is the ability to build up to ten rows of 100 beads, allowing for students to replicate our demonstration rekenrek and use it. The bead order can be reversed (red-white or white-red), and a shade is provided, which is great for illustrating missing addend problems. There is a keypad and pen and for creating expressions and equations, as well as circling groups of beads. Using the app in conjunction with student instruction make it a useful tool during guided lessons as well as independent learning activities.
The Number Rack app worked really well in conjunction with instruction through the Bridges 2 curriculum. I would second the comments made by the app reviewer "...you'd benefit from a good search for abacus lessons (search for "slavonic abacus", "bead-frame", "rekenrek," and "100-bead abacus" lessons) before jumping into classroom or one-on-one use, because without some support it's pretty tough to discover number properties just by playing around" With a solid understanding of the purposes and procedures in the use of rekenreks, this app is a great tool. It is definitely not something you could give to a student without instruction. The app does include instructions on the various features of the app which are clear and helpful. All in all, this app is a good tool for students with background instruction, and it provides an opportunity for the reflective teacher to become more educated in the number and pedagogical theory behind its use. (Hence the time for set up being more than 15 minutes. Otherwise, it's download and go.)