Inside a kindergarten classroom with Augustana students

Digi-Blocks Help Explain Teen Numbers!

Blog 7

This past week we worked with a few students to strengthen their understanding of teen numbers with the use of Digi-blocks. We found these were extremely helpful for kindergarteners to visualize the meaning of teens as a “group of ten and some more”. First we showed the box of 100 blocks to the student and asked him to count how many medium sized boxes were inside. The students responded with 10, and quickly opened one of the boxes to find there were also ten small blocks inside. The kindergartener then counted by tens to find there were 100 blocks total. We were then able to use this knowledge that there were 10 in each box to aid student in his understanding of teen numbers.

I asked the first student we worked with to show the number 14 using the small blocks. So we emptied out a few medium sized containers and the student began counting out 14 pieces. For this “game”, we told the student that we want to determine how many medium boxes we can fill up with small pieces. The student replied that, “10 will fit!”. So he put 10 small pieces into the medium box, and closed the lid so that he knew no more could fit. He then realized that there were “4” extra. We then had the student use the number cards to represent how many blocks were shown. He placed the number 10 card next to the completed medium sized box, and the number 4 card next to the “extras”. We then asked the student how many blocks were there total, and he repeated that he had “10” and “4”. I told him that yes that was correct, but we wanted to know how many he had all together.  The student looked confused, even though he had earlier told us that a full box has ten pieces, and began re-counting all the blocks.

It was interesting that the student knew exactly how many pieces were in each group, but combining them together and counting on from 10 proved to be the most difficult. I referred the student back to their number cards and said, “Well instead of re-counting the blocks, let’s look at the number cards.” The student said, “10 and 4”. I nodded my head in agreement, and said, “right and if we combined both groups together, we would have…”. The student took the two number cards and pushed them together like we had practiced before so that the 0 in the 10 was being covered by the 4 to make 14. The student responded, “14”. I wanted the student to make sure they knew what “a completed medium box” represented, so I added another group of 10 and asked the student what number would now be represented. Surprisingly, the student said, “2 groups of 10 and 4 extra”. He even used the same terms of “groups and extra” we had modeled to him earlier when provided evidence of application of knowledge. We counted with the student to realize there would now be 24 blocks.

I think the use of digi-blocks to model understanding of teens really helped many of our students. However, I did think about one misconception that may be forming as the result of our other ideas to illustrate addition. To introduce teen numbers before the digi-blocks, we have been showing the students a “10” number card and a single digit, to overlap the cards and show a teen number “10 and 5 = 15” for example. However, I wonder if this habit of using the number cards to combine groups and check their answers, will transfer over to other addition. I am hoping the students are beginning to develop a strong enough understanding of the single digit numbers to know that for example, the 4 and 5 cards cannot just be smooched together to make 45.  Although I think the students will be fine if we stress that this is simply a trick used with 10s and our “special teen numbers”, not when adding any two groups.

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