Unit Plan 14 (Grade 1 Math): Add/Sub within 100—Models to Methods
Add and subtract two-digit numbers within 100 (no regrouping) using place-value models, drawings, and number lines; match equations to models and explain strategies.
Focus: Add and subtract two-digit numbers without regrouping using tools and drawings; explain why strategies work.
Grade Level: 1
Subject Area: Mathematics (Number & Operations in Base Ten)
Total Unit Duration: 5 sessions (one week), 45–60 minutes per session
I. Introduction
Students connect place-value structure to addition and subtraction within 100 without regrouping. They model with base-ten blocks, quick tens/ones drawings, and open number lines, then record equations that match their models. Emphasis is on precision, clear representations, and choosing an efficient method.
Essential Questions
- How does place value (tens/ones) help me add or subtract without regrouping?
- How can blocks, drawings, or number lines prove my answer?
- How do I choose a clear and efficient method for a problem?
II. Objectives and Standards
Learning Objectives — Students will be able to:
- Represent two-digit numbers as tens and ones and explain no-regroup cases.
- Add/subtract within 100 without regrouping using blocks, drawings, and open number lines.
- Record equations that match models and label work with units and symbols.
- Explain and check answers for reasonableness using place-value language.
Standards Alignment — CCSS Grade 1 (threaded across the unit)
- 1.NBT.4: Add within 100 using concrete models or drawings and place-value strategies; relate the strategy to a written method (no regroup in this unit).
- Mathematical Practices: MP.4 (Model with mathematics), MP.6 (Attend to precision) emphasized; MP.7 threaded.
Success Criteria — Student Language
- I can build/draw a problem and show tens and ones.
- I can add or subtract within 100 without regrouping and write an equation that matches my model.
- I can explain why my answer makes sense using place value.