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missjmathed.bsky.social
@missjmathed.bsky.social
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missjmathed.bsky.social
I know I am a little late to the party but a Rekenrek would work really well for modeling this strategy. Instead of counting back and subtracting 3 from the bottom and 2 from the top, you just subtract the 5 from the top row (which is your 10). Helps visually show why you have to add the 3 back.
The top image shows a 20 bead Rekenrek. On the top row, 10 beads are pushed to the left but a gap has been left in between the 5 red and 5 white beads. A hand written 10-5 is shown. On the bottom row 4 red beads are pushed to the left. A circle is drawn around the 9 red beads on the left and 9 is hand written. The bottom image also shows a 20 bead Rekenrek. 10 beads have been pushed to the left but a gap has been left between 2 red beads and a group of 3 red and 5 white beads. A handwritten 10-8 is written. On the bottom row 3 red beads are pushed to the left. The 2 red beads and 3 red beads are circled and label with the number 5.
December 14, 2024 at 12:43 AM