Number Rack, by The Math Learning Center
Virtual abacus works just like the real thing, not as fun
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Number Rack, by The Math Learning Center
Pros: Looks and feels like a physical abacus with responsive controls and familiar layout, while annotation features and variable rows add extra value.
Cons: Colors are fixed, there's no built-in lessons or guides, and there's no satisfying "click" when sliding beads around. Plus, use is totally reliant on teacher knowledge.
Bottom Line: It's a free, portable abacus that requires a good curriculum to make it useful. Otherwise it's just e-beads.
Incorporate Number Rack into your early counting and place-value lessons to add that great manipulative boost to otherwise tough cognitive jumps. Also, even older kids can benefit from the way it makes multi-digit addition and subtraction so real and present, in a way that carrying and borrowing in tabular arithmetic can't quite touch.
Either way, 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. If you've already got a physical version, go with that first; if you want every kid to have their own to work with, installing this on a class set of tablets would be a smart move.
Number Rack is a virtual slavonic abacus (also called a bead frame) with some extra features that make it a more flexible learning tool than the real deal. It features the familiar red and white beads (which can't be re-colored) and horizontal layout of the elementary school manipulative, and beads slide across the virtual rods effortlessly with smooth animation. Groups of beads can be dragged and positioned arbitrarily, just like the real thing.
Unlike the physical version, Number Rack lets users change the number of rows, from just one (to two if you need a 20-bead rekenrek), all the way up to the classic 10. It also includes an annotation tool so you can write notes and circle groups, and an equation editor for adding math right to the screen. There's a built-in shade so you can cover groups of beads in pre-set arrangements.
The 100-bead abacus has a long history of elementary school use, and Number Rack's version will work just as well as that real-life learning tool. It's great for teaching place value, counting patterns, multi-digit operations, and grouping, to name just a few applications. This one doesn't have the wonderful hands-on feel and satisfying click-clack of physical beads, and there is some emotional, intuitive sense of number lost in the translation to a virtual tool, so don't chuck out your wooden model just yet.
The option to change colors to make it resemble a Montessori-style bead frame, or to color groups of beads arbitrarily for specialized lessons, would add extra value beyond the typical slavonic abacus uses. Also, even a little bit of support for kids and teachers about how to use this fairly specialized tool would be a welcome addition.
Learning Rating
A Virtual Abacus for the Internet Age
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.)
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