Course Discussion: Module 3, Five is Prime

Core Curriculum The Abacus: A Million Manipulatives in Your Pocket
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Five is Prime

  1. What strategies will you use with current students when they are reading braille or large print worksheets? Do you have additional suggestions of strategies? I like the suggestions for placement of the pen specifically in their dominant hand for ease of use when writing their answers. Also, I think that reading the whole problem through first and reading it outloud would be helpful so that the instructor can hear what the student is reading and check for accuracy, but also the student gets an idea of the numbers and signs prior to starting the equation on the abacus.

  2. Create an addition and subtraction problem for the purpose of teaching the complements of five. Be sure to include at least five single digits. 2+3-4+6-3

  3. A student completes the problem 4 + 15 + 9 + 21 and writes the answer 44 on the paper. Explain which common error the student made and how you would address this in your next lesson. The error may be due to the student only reading the lower beads and forgetting to check the beads above. I would have the student reread their abacus in the moment and see if they still agree with the answer that they wrote down. If not, I would have them re-do the problem and check their work to see if their answer agrees with what they wrote down or what they have on their abacus. In a next lesson, the instructor could position the beads and then have the student practice reading what the beads add up to. Since they do not have any background information of inputting numbers into the abacus, they are truly just practicing figuring out the total on the abacus by feeling the beads. Then continue working on equations that incorporate answers that involve incorporating the upper beads.

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I have a student that uses an iPad to self enlarge materials, I will have the iPad on his right side and the abacus on his left due to the fact that he also has right hemiparesis CP and has limited use of his right hand, so he is a left handed abacus user.

2 + 3 + 5 + 7 + 8 – 5

Student’s work:
4 + 15 + 9 + 21 = 44

Correct answer:
4 + 15 + 9 + 21 = 49

Error type:
This is most likely a place value or carrying error, a common mistake in addition where the student forgets to “carry” a ten from the ones place to the tens place.

Possible reasoning:

  • 4 + 15 = 19

  • 19 + 9 = 28

  • 28 + 21 = 49
    The student likely added 28 + 21 incorrectly (possibly 28 + 16 = 44 or miscounted by 5).

Next lesson focus:

  • Review place value addition strategies especially how to regroup or carry when sums exceed ten.

  • Use base-ten blocks or number lines to make the regrouping visible.

  • Model step-by-step addition:

    • Add the ones first, regroup if necessary,

    • Then add the tens.

  • Reinforce complements of five and ten to help students check their mental math:

    • For example, 9 + 1 = 10, 8 + 2 = 10.