A rekenrek is one of my favorite early elementary math manipulatives. First designed by Adrien Treffers from the Freudenthal Institute in Holland, a rekenrek is a set of 20 beads organized into two rows of 10, with 5 red and 5 white beads on each row.
You can easily create and recognize each number from 1 – 20 using the groups of 5 beads. For example, if I push the whole first row to the left and 2 beads on the bottom row, I can quickly recognize the number 12.
The ability to “see” numbers rather than counting them is called subitizing and is an important early indicator of number sense. Normally we are only able to subitize small numbers (1-4), but the rekenrek helps children quickly see larger numbers as combinations of sets. For example, I can quickly see that there are 8 beads if I see 5 red beads and 3 white. I could also show this with linker cubes, but it takes a lot longer to count out and construct stacks of linker cubes.
The rekenrek is also a quick way to demonstrate and practice addition strategies. You can demonstrate counting on with the problem 6 + 3 by first sliding over 6 beads as a group, saying “6,” and then sliding over three more beads individually, “7, 8, 9.” Remember to say “7, 8, 9” rather than “1, 2, 3” as you are sliding over the beads.
You can practice near doubles (or doubles plus one) by first creating a doubles problem such as 4 + 4, by sliding over 4 beads in each row. Then slide over one more bead on the top row to create 5 + 4 or one more bead on the bottom to create 4 + 5.
Demonstrating near tens is easy on the rekenrek. Let’s say you’re trying to solve the problem 8 + 4, first slide over 8 on the top row. Then slide over 2 on the top to complete the 10 and 2 more on the bottom to make 12.