Do you need ideas for teaching how to add 9 to a single digit number? While I was creating my Monkey in the Middle addition fact strategy resources, I decided using cube towers or rods would also be perfect for demonstrating in a concrete way how and why you can Make a 10 to Add 9.
Once I started working on this, I realized that when Making a 10 using the cube towers, you subtracted one from the other addend. However, the anchor charts and flashcards, indeed all my other materials for The 9 Rule focus on Making a Ten, adding, and then subtracting one from the sum! Hmmm…
I wasn’t quite sure what to do! A bit of contemplating and a little research confirmed that both approaches were valid.
So, I created two different resources, one for each method. Everyone learns in different ways. Choose the one that makes the most sense to you. Or teach both and follow your learners’ lead. Both resources include the following verbal cues, “See 9. Think 10. Hop back 1.”, along with a frog as a visual cue.
One Way to Introduce the Add 9 Strategy
Use this free concrete introductory activity to show how and why the Add 9 strategy works. Make sure your students are fluent in adding 10 to a single digit number. Teach by modeling it in a small group or projecting it for a whole class.
- Choose to print the color or black/ white pages.
- Decide if students will work individually or in pairs.
- Print one open-ended cube mat for each student or pair of students. Use card stock and laminate for durability.
- Print one teacher copy of the Add 9 equation cards.
- Provide 2 sets of 10 multi-link cubes (the ones that link on all sides) in 2 different colors for each student or pair of students.
- Choose an equation card.
- Use two colors of cubes to show the numbers in the equation on your mat.
- Write the equation on your mat.
- Verbalize: See 9. Think 10.
- How can we make the 9 a 10?
- Model moving one cube from the addend that is not 9 to the rod with 9 to Make It Ten.
- Write the new Add 10 equation.
- Which equation is easier to add?
- Emphasize that you still have the same number of total cubes and the two equations are equal or equivalent.
- Repeat with multiple equations.
Write on the laminated mats with dry erase markers. To reuse mats that are not laminated, write the equations on a separate piece of paper or a dry erase board.
Once you have introduced this activity, it can be repeated in a center.
Click on the highlighted words, The 9 Rule Addition Fact Strategy Sample, to download this free resource from my TpT store.
Looking For More Resources
Using this free resource will provide enough instruction for some of your students to apply this strategy to Add 9 to a single digit number. Other students will need different degrees of practice and review to become successful.
I created a more complete set of resources, The 9 Rule Addition Fact Strategy, to help meet their needs. This set is also based on subtracting one (or hopping back) from the second addend to change the 9 to a 10 and then adding to find the sum. The focus is on recognizing equivalent Add 9 and Add 10 equations.
Try the equation cube mats, another concrete level activity, in a small teacher-directed group or as an independent math center. The matching cube cards with a recording sheet provide practice at a pictorial level.
Match the Add 9 equations with their equivalent Add 10 equations to increase automaticity with this strategy.
For additional practice, use the worksheet as morning work, seat work, or homework.
Applying The 9 Rule correlates with all of my other resources that include this addition fact strategy. This set of activities is based on changing the 9 to a 10. Adding and then subtracting (or hopping back) 1 from the sum. The focus is on following specific steps to find the sum.
Engage your students with the hands-on practice activities for changing the 9 to 10 using equation cards and fun frog number cards.
Provide step-by-step practice in applying the strategy with the follow-up worksheets.
Check out the Addition & Subtraction section of my Teachers Pay Teachers store for even more resources, including anchor charts, flashcards, and worksheets.
Read more blog posts about addition fact strategies.
Comment below to share how you teach this addition fact strategy.
Title photo image is by roni kurniawan.