1st Grade Math: Adding Within 20 Using Ten Frames and Decomposition Strategies
Support your First Grade students as they learn to add within 20 using two developmentally appropriate strategies: Ten‑Frames and Decomposition. Each strategy is taught in two parts; first with problems where both addends are less than 10, and then with problems where one addend is greater than 10. This structure helps students see how the thinking changes depending on the numbers, and it builds a strong foundation for mental math.
Strategy 1: Adding with Ten‑Frames
Students begin with a visual, concrete approach to making 10. They learn how to use ten‑frames to organize quantities, see the missing part to 10, and add the leftover.This strategy is taught in two cases:
Case A: Both numbers are less than 10
Students use ten‑frames to make 10 and add the leftover part.
Case B: One number is greater than 10
Students use ten‑frames to show the teen number as 10 + leftover, then add the second number.
This section includes guided examples, scaffolded practice, and mixed pages to build fluency.
Strategy 2: Adding with Decomposition
After working with ten‑frames, students transition to symbolic thinking.
In this strategy, students add within 20 by decomposing one number to make the addition easier.
This strategy is also taught in two cases:
Case A: Both numbers are less than 10
Students decompose one addend to make 10.
Case B: One number is greater than 10
Students decompose the teen number into 10 + leftover, then add the leftover to the second number.
Students learn to reorganize numbers flexibly, compose new numbers, and write equations that match their thinking.
✨ What’s Included
Teacher notes to introduce the strategies
Strategy 1: Ten‑Frames
Ten‑frame review
- Guided examples for both cases
- Scaffolded practice pages
- Mixed practice
Strategy 2: Decomposition
- Strategy overview
- Guided examples for both cases
- Optional decomposition mat
- Two worked examples using the mat
- Step‑by‑step strategy pages
- Practice worksheets
🎯 Perfect for
- First grade addition within 20
- Small‑group instruction
- Intervention and reteaching
- Math centers
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Hi, I'm Elizabeth! I'm a retired educator with a love for playful, purposeful learning. I create literacy, math, and SEL resources for lower elementary levels because I want to support teachers who may feel overwhelmed by planning and want low-prep activities that are easy to use and fun to teach.
💜 In case you're wondering why my store is named PurpleLog - it was the name of my original educational company years ago, when I developed enrichment programs for schools across Singapore. The name itself comes from a fantasy story I created for my children when they were very young, all about a magical forest filled with purple logs. They loved it, and as they grew into wonderfully creative adults, the name became a meaningful reminder of those early stories and the joy of inspiring imagination. Today, I continue that spirit through the resources I create, hoping to spark the same sense of curiosity and creativity in children.
