Unit Plan 29 (Grade 1 Math): Add/Sub within 100—No Regrouping Fluency

Focus: Solidify mental strategies and written methods for addition and subtraction within 100 without regrouping (tens/ones structure, expanded form, and open number lines).

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 strengthen fluency for two-digit addition/subtraction without regrouping by leveraging tens-and-ones structure, expanded form, and open number line jumps. Emphasis is on seeing and using structure to choose efficient strategies and explain why they work.

Essential Questions

• How does tens/ones structure help me add or subtract within 100 without regrouping?
• When should I use expanded form, vertical methods, or an open number line?
• How can I explain that my method is efficient and correct?

II. Objectives and Standards

Learning Objectives — Students will be able to:

1. Add and subtract two-digit numbers within 100 without regrouping using tens/ones structure.
2. Represent thinking with expanded form, base-ten models, and open number line jumps by tens then ones.
3. Use 10 more/10 less and subtract multiples of 10 as mental strategies.
4. Record vertical and horizontal equations clearly and check for reasonableness.
5. Explain why a method works by referring to place value and structure (MP.7).

Standards Alignment — CCSS Grade 1 (threaded across the unit)

• 1.NBT.4: Add within 100 using concrete models/drawings and strategies based on place value; relate strategies to a written method.
• 1.NBT.5: Mentally find 10 more/10 less than a two-digit number; explain reasoning.
• 1.NBT.6: Subtract multiples of 10 from two-digit numbers using place-value strategies.
• Mathematical Practices: MP.7 emphasized; MP.1, MP.6 threaded.

Success Criteria — Student Language

• I can separate tens and ones and compute without regrouping.
• I can show my work with expanded form or an open number line and explain each step.
• I can use 10 more/10 less and subtract multiples of 10 to solve quickly and check my answer.