Course Discussion: Module 2, The Complementary Abacus

The Complementary Abacus

  1. Previously, when did you typically introduce a calculator to your students? What might you do differently now?

  2. Create an addition and subtraction problem for the purpose of teaching the compliments of ten. Be sure to include at least five single digits.

  3. Write a script describing the steps of adding nine to six.

  1. I usually introduce the calculator in 5-6 grade in preparation for when they will be able to use it on state testing, unless student need dictates otherwise.

  2. 6+9+3-7-5

  3. Set 9
    Set 10
    Clear 6 complementary number; 4
    Answer: 15

Hi Lynda!
You problem is spot on for practicing addition and subtraction using complements of 10. Your instructions are short and sweet but I bet students would like it that way.

  1. I typically introduce a calculator around fifth grade, sometimes before if their class is using them, then I would introduce before. It really is dependent on the student and what is happening in their classroom.

  2. 6+5+3-2

  3. Set 6
    add 5- the pair’s equivalent is 5;
    move over to tens place and set 10
    add 3 in the ones
    subtract 2
    answer 12

Hi Melissa!
Your problem does have an addition complement of 10. Nice work. I see you explained your own problem in #3 (sort of). In your instructions for your own problem you do not indicate removing the 5 bead from the ones column after you set the one bead in the ten’s column.

Do you want to try writing a script describing the steps of adding nine to six?

I am not a teacher yet but I feel like a calculator wasn’t introduced to me until middle school or late elementary.

7 + 3 - 5 + 6 - 2

Start with 7
Add 3: 7+3=10
7+3=10 (This demonstrates the complement of 7 and 3 making 10)
Subtract 5: 10−5=5
Add 6: 5+6=11
Subtract 2: 11−2=9
Final result: 9

  1. Previously, I introduced a talking calculator to my students at a young age, to check calculations done on their braille writer or abacus. However I didn’t provide them an abacus to use in class until the same time as their peers - about 6th grade. I don’t think I would change when I teach these skills.
  2. 8+7-5+4-2 = 12
  3. Write a script describing the steps of adding nine to six.
    We are going to add 9+6. We will start by first setting nine in the ones column of the abacus. Set nine by pushing a 5 bead down and 4 ones beads up. Now that we have our 9 set, we can add 6. To add 6, we look at the ones column, and notice that there are no beads for us to to set. This means that we will go to the tens column, and push up 1 ten bead. Now we have to ask ourselves, what is the complement of 10 and 6? It’s 4! We will clear (or push down) 4 ones beads from the ones column. This should leave us with 1 ten, and 5 ones, which is 15, so our sum is 15.

Hi nieberding.28, your problem is actually quite complex with multiple complementary number movements. At this time you and your student have only learned the complements of 10. I suggest 7 + 3 + 5 + 3 - 2 so your student has more success.

Hi appleton.thea, would you still wait until sixth grade to introduce the abacus?
Your problem is a great introduction to the complements of 10 for your student.

Ooops! That was a mis-type!
I start showing them a basic abacus in preschool for counting. We work on abacus a lot more in elementary, and some students choose to use it in class. Some students fight it. I introduced a talking calculator to my students at a young age, as a way to check calculations done on their braille writer or abacus. However, I didn’t provide them a TALKING CALCULATOR to use at-will in class until the same time as their peers - about 5th or 6th grade. I don’t think I would change when I teach these skills.

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