Recognizing to 20 on rekenrek

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Students learn what a rekenrek is and can recognize numbers 11-20.

K.CC.B.4

K.CC.B.5

Discuss with students that by recognizing numbers on the rekenrek they are able to calculate faster. They don't need to count every bead to know which numbers is being represented. Using the rekenrek also makes it easier to solve adding to/taking from problems.

Name the numbers from 11-20 and ask students to write them down. The students can hold up their answers so you can check their work. Show two rekenreks and ask which one shows 6 beads.

Explain what a rekenrek looks like. Show that the top and bottom rows both have five red and five white beads. Discuss how to use a rekenrek. It is important that the red beads are to the left and the white to the right. Before you begin using the rekenrek, all beads should be moved to the right. Next give an example which shows how you count beads on the left side. Tell students that you count on from the number from the top row. The top row has 10 beads. Count on to the bottom row. Start with the red beads. You'll end up at 15. There is 1 white bead left, so 16 beads total. Afterwards, ask students of they know how many beads are on the rekenrek. They can choose from the given numbers, but must write down their answers.

Check that the students can recognize numbers to 20 on the rekenrek with the following questions:

What does a rekenrek look like?

Are there more red or white beads or are they the same amount?

How do you know which number is on the rekenrek?

Students start with an exercise with two possible answers. Next there are three possible answers, and finally they must write down the number shown on the rekenrek by themselves.

Check that students understand that a rekenrek has groups of five red beads and five white beads. Emphasize that it is useful to recognize numbers on a rekenrek, to increase calculation speed. To check understanding, ask students to form numbers that you give on their own rekenreks

Students who have difficulty with recognizing numbers on the rekenrek will likely have difficulty counting to 20. Have these students practice with the rekenrek by counting the beads one by one.

Rekenrek

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