# Course Discussion: Module 2, The Complementary Abacus **URL:** \ **Category:** Adding and Subtracting with the Abacus\ **Created:** [December 18, 2023, 8:29pm UTC](https://community.aphhive.org/t/course-discussion-module-2-the-complementary-abacus/839 "2023-12-18T20:29:28Z")\ **Posts on this page:** 14\ **Page:** 2
**Author:** ![LeanneGrillot](https://sea1.discourse-cdn.com/flex015/user_avatar/community.aphhive.org/leannegrillot/32/110_2.png) [@LeanneGrillot](https://community.aphhive.org/u/LeanneGrillot)\ **Post date:** [May 29, 2025, 12:43pm UTC](https://community.aphhive.org/t/course-discussion-module-2-the-complementary-abacus/839/21 "2025-05-29T12:43:23Z")
Hi @tpeterson Your problem is a challenging one as it practices many complements of 10! I appreciate your descriptive text teaching a student how to add 9 + 6. ---
**Author:** ![LeanneGrillot](https://sea1.discourse-cdn.com/flex015/user_avatar/community.aphhive.org/leannegrillot/32/110_2.png) [@LeanneGrillot](https://community.aphhive.org/u/LeanneGrillot)\ **Post date:** [May 29, 2025, 12:45pm UTC](https://community.aphhive.org/t/course-discussion-module-2-the-complementary-abacus/839/22 "2025-05-29T12:45:25Z")
Hi @Michelle_Ellis Your problem would be considered and intermediate level complements of 10 problem as it has a few complement movements, but not for each addend. ---
**Author:** ![LeanneGrillot](https://sea1.discourse-cdn.com/flex015/user_avatar/community.aphhive.org/leannegrillot/32/110_2.png) [@LeanneGrillot](https://community.aphhive.org/u/LeanneGrillot)\ **Post date:** [May 29, 2025, 12:48pm UTC](https://community.aphhive.org/t/course-discussion-module-2-the-complementary-abacus/839/23 "2025-05-29T12:48:30Z")
Hi @Mary_Tubilleja I love the idea of pairing the abacus and calculator together. Your problem has complements of 10 and it fine up until you try to add the 7. At this point you are moving beyond complements of 10. I would suggest changing the 7 to a 9 and then adding 3 instead of subtracting 3. This would be 2 + 8 - 4 + 9 + 3 ---
**Author:** ![LeanneGrillot](https://sea1.discourse-cdn.com/flex015/user_avatar/community.aphhive.org/leannegrillot/32/110_2.png) [@LeanneGrillot](https://community.aphhive.org/u/LeanneGrillot)\ **Post date:** [May 29, 2025, 12:50pm UTC](https://community.aphhive.org/t/course-discussion-module-2-the-complementary-abacus/839/24 "2025-05-29T12:50:22Z")
Hi @sarah.whittington I am so happy the abacus is gaining value in your eyes. You also have an excellent beginner complements of 10 problem. ---
**Author:** ![LeanneGrillot](https://sea1.discourse-cdn.com/flex015/user_avatar/community.aphhive.org/leannegrillot/32/110_2.png) [@LeanneGrillot](https://community.aphhive.org/u/LeanneGrillot)\ **Post date:** [May 29, 2025, 12:52pm UTC](https://community.aphhive.org/t/course-discussion-module-2-the-complementary-abacus/839/25 "2025-05-29T12:52:59Z")
Hi @Kim_Shoffner You have a creative way of incorporating the calculator and the abacus in one lesson. Your example complements of 10 problem is quite complex and would be given when a student has learned many complements already. You gave an excellent description of the steps in your own problem. What would be the steps for adding nine to six? ---
**Author:** ![LeanneGrillot](https://sea1.discourse-cdn.com/flex015/user_avatar/community.aphhive.org/leannegrillot/32/110_2.png) [@LeanneGrillot](https://community.aphhive.org/u/LeanneGrillot)\ **Post date:** [May 29, 2025, 12:55pm UTC](https://community.aphhive.org/t/course-discussion-module-2-the-complementary-abacus/839/26 "2025-05-29T12:55:12Z")
Welcome to the Hive @jfbamber I have added a few calculator activities to my toolbox - thanks for the ideas! Your complements of 10 problem is great for isolating the 4-6 partners of 10. ---
**Author:** ![Kim\_Shoffner](https://avatars.discourse-cdn.com/v4/letter/k/46a35a/32.png) [@Kim\_Shoffner](https://community.aphhive.org/u/Kim_Shoffner)\ **Post date:** [May 29, 2025, 7:51pm UTC](https://community.aphhive.org/t/course-discussion-module-2-the-complementary-abacus/839/27 "2025-05-29T19:51:34Z")
To add 9 to 6, set 6 on the abacus by pinching the 5 bead with the right pointer finger down toward the separation bar and the one bead with the right thumb up toward the separation bar at the same time. I do not have 9 to add to the first column so I would make a ten pair compliment exchange by setting a one bead in the second column by pushing it up with the right thumb toward the separation bar and removing 9’s ten pair compliment of 1 in the first column by pushing down a one bead with the right pointer finger. I read the answer as 15. ---
**Author:** ![LeanneGrillot](https://sea1.discourse-cdn.com/flex015/user_avatar/community.aphhive.org/leannegrillot/32/110_2.png) [@LeanneGrillot](https://community.aphhive.org/u/LeanneGrillot)\ **Post date:** [May 30, 2025, 1:12pm UTC](https://community.aphhive.org/t/course-discussion-module-2-the-complementary-abacus/839/28 "2025-05-30T13:12:14Z")
Hi @Kim_Shoffner You have wonderfully descriptive steps in your instructions for adding 9 to 6. Want to try your hand and creating a math problem that teaches the complements of 10? ---
**Author:** ![Kim\_Shoffner](https://avatars.discourse-cdn.com/v4/letter/k/46a35a/32.png) [@Kim\_Shoffner](https://community.aphhive.org/u/Kim_Shoffner)\ **Post date:** [May 30, 2025, 10:10pm UTC](https://community.aphhive.org/t/course-discussion-module-2-the-complementary-abacus/839/29 "2025-05-30T22:10:20Z")
7 + 9 + 5 = 21 I set 7 on the abacus by pinching the 5 bead down toward the separation bar with the right pointer finger and pinching the 2 one beads up toward the separation bar with the right thumb at the same time in the first column. I do not have 9 to set in the first column so I set one bead in the second column by pushing it up toward the separation bar with the right thumb. I remove 9’s 10 pair compliment 1 in the first column by pushing it down away from the separation bar with the right pointer finger leaving the subtotal 16. The 5 bead is already set in the first column so I have to set a one bead in the second column by pushing it up toward the separation bar with the right thumb and removing 5’s 10 pair compliment 5 by pushing the 5 bead in the first column up away from the separation bar with the right pointer finger. I read the answer 21. ---
**Author:** ![LeanneGrillot](https://sea1.discourse-cdn.com/flex015/user_avatar/community.aphhive.org/leannegrillot/32/110_2.png) [@LeanneGrillot](https://community.aphhive.org/u/LeanneGrillot)\ **Post date:** [June 2, 2025, 5:16pm UTC](https://community.aphhive.org/t/course-discussion-module-2-the-complementary-abacus/839/30 "2025-06-02T17:16:40Z")
Nice work, @Kim_Shoffner Your problem has two complements of ten, the 9 and 1 and the 5 and 5. ---
**Author:** ![Juliana\_Morris](https://avatars.discourse-cdn.com/v4/letter/j/f14d63/32.png) [@Juliana\_Morris](https://community.aphhive.org/u/Juliana_Morris)\ **Post date:** [July 27, 2025, 2:56am UTC](https://community.aphhive.org/t/course-discussion-module-2-the-complementary-abacus/839/31 "2025-07-27T02:56:32Z")
1. I am currently in school to receive my TSVI certification, so I do not have any current visually impaired students. However, I think it would make sense to introduce around 5th or 6th grade due to the TEKS on the STAAR test. 2. 9+6+3-5-7 3. Set 6, add 10, clear the compliment of 9 (1). Answer = 15 ---
**Author:** ![Susan\_Knauff](https://avatars.discourse-cdn.com/v4/letter/s/da6949/32.png) [@Susan\_Knauff](https://community.aphhive.org/u/Susan_Knauff)\ **Post date:** [August 11, 2025, 12:59am UTC](https://community.aphhive.org/t/course-discussion-module-2-the-complementary-abacus/839/32 "2025-08-11T00:59:11Z")
The Complementary Abacus 1. I have not worked with young students. I worked with adults who were adventitiously visually impaired as adults, so they had sight throughout their school years. 2. 6+5+9-5+3 3. Write a script describing the steps of adding nine to six. Set 6 by pinching the 5-bead and the one bead in the first column. You do not have enough beads in the first column to add 9, so to add 9, set the 10 bead in the second column. The complement of 9 would be 1, so clear one bead in the first column. Answer: 15. ---
**Author:** ![June\_Allison](https://avatars.discourse-cdn.com/v4/letter/j/c57346/32.png) [@June\_Allison](https://community.aphhive.org/u/June_Allison)\ **Post date:** [November 4, 2025, 8:28pm UTC](https://community.aphhive.org/t/course-discussion-module-2-the-complementary-abacus/839/33 "2025-11-04T20:28:39Z")
I previously worked in a high school Extended Content Standards setting and taught all of my students grades 9-12 how to use a calculator. 7+3+4+6+9−1−8 Set 6 Add 10 take away 1 Answer is 15 ---
**Author:** ![Brigit\_Jensen](https://avatars.discourse-cdn.com/v4/letter/b/48db29/32.png) [@Brigit\_Jensen](https://community.aphhive.org/u/Brigit_Jensen)\ **Post date:** [September 23, 2026, 2:15pm UTC](https://community.aphhive.org/t/course-discussion-module-2-the-complementary-abacus/839/34 "2026-09-23T14:15:01Z")
The Complementary Abacus 1. Calculators are typically introduced in 6th grade. They cannot use them on state testing before 7th. But an abacus could be used. 2. 3+8-2+4-5 3. Set 6 (pinch a 1 and 5 bead), add nine by adding a ten bead and removing nine’s compliment of 1. Now you have a 1 in the ten’s column and a 5 in the one’s column. 15 [Previous page](https://community.aphhive.org/t/course-discussion-module-2-the-complementary-abacus/839.md?page=1)