It’s the time of year when teachers start looking forward to the upcoming school year. Me? I’ve been thinking about number sense.
Number sense–the meaning of numbers, their magnitude, the relationships between them–forms the foundation for math thinking. Students with strong number sense are able to reason with numbers and solve problems in flexible ways.
The rekenrek is one tool that can help students stengthen their number sense. Use of this “arithmetic rack” supports students in their development of efficient counting strategies as well as an understanding of teen numbers. It also helps them become fluent with addition and subtraction strategies, including the use of doubles, doubles + 1, and making 10s.
Buying class sets of rekenreks, however, can be costly. So I set out to find a way to make my own–rekenreks that are sturdy, have beads that slide easily, and that are cheap and easy to make. Here’s what I came up with!
For each rekenrek, you’ll need two erasers and two 10″ bamboo skewers as well as 10 red and 10 white 9mm pony beads. I found packs of 5 erasers for $1 at Office Max and got two bags pony beads at Michael’s for about $6 with a discount coupon. Target carries bags of 80 skewers for about $2.
To make them, you’ll need an electric drill, 1″ wide tape, and a little nipper tool. Don’t let the electric drill intimidate you–I’d never used a drill before, but was able to do this project easily. You might also want a ruler and a marker.
The first steps you can do assembly-line fashion.
Step 1: Tape sets of 2 erasers together. By doing this, you can make sure that drill holes for each rekenrek are aligned. Also, because you want the skewers about 1″ apart, you can use the tape as a drilling guide. One more tip: tape them together so they look like a chevron. This will make it easier to assemble them in Step 5.
Step 2: Drill two holes into each set of erasers. Choose a drill bit that is as close to the diameter of your skewer as possible. If you have to, use a bit that is a little smaller than your skewer. There’s enough give in the erasers that you should be able to ease the skewers in. If you use a larger bit, the skewers may slide out of the eraser.
I used the tape and first/last letters in the store logo as drilling guides. If you want to be more precise, you can measure and mark them. Set the taped erasers on a block of wood to protect the table beneath. Holding the drill level, drill down until you hit wood and then reverse the drill to get it back out.
The last steps need to be completed for each rekenrek. If you do these steps assembly-line fashion, it will be harder to keep the sets of erasers with their aligned drill holes together.
Step 3: Using the pointed tip, slide the skewers into the drill holes in one eraser. When you do this, hold the skewer near the tip and ease it in. If you hold near the far end, the skewer is more likely to break. Keep sliding until there is about 1/4 inch of skewer left sticking out at the end of the eraser.
Step 4: Add 5 red beads and 5 white beads to each skewer.
Step 5: Slide the skewers into the drill holes on the second eraser. Here’s where taping the erasers into a chevron shape comes in handy. To align the drill holes in the second eraser, simply make sure that the erasers still form a chevron. Then use the nippers to clip the pointed ends of the skewers.
Tada! Repeat until you have made a class set. Making a class set of 25 rekenreks–including going out to buy supplies–took just one afternoon and cost less than $20!
Anonymous
Clever!