Printable Addition and Subtraction Within 20 Math Worksheet

This comprehensive 4-page math worksheet provides structured practice for mastering addition and subtraction within 20. By focusing on mental math strategies like "making 10" and decomposition, it helps learners build early elementary fluency. Students transition from scaffolded equations to independent word problem solving, ensuring a thorough understanding of basic operations.

At a Glance

• Grade: 1 · Subject: Math
• Standard: 1.OA.C.6 — Add and subtract within 20 using strategies like making ten and decomposing numbers
• Skill Focus: Addition and subtraction strategies and fluency
• Format: 4 pages · 18 problems · Answer key included · PDF
• Best For: Small group instruction or independent math centers
• Time: 20–30 minutes

This resource includes four sections designed to build conceptual understanding. The first pages focus on addition, utilizing frames for "making 10" and adding three addends. The third page covers subtraction via splitting numbers, while the final page features real-world word problems. A self-reflection tool and a full answer key are included.

Skill Progression

• Guided Practice: Features "Making 10" addition frames with step-by-step numeric scaffolds to reduce cognitive load.
• Supported Practice: Includes strategy prompts for adding three numbers and subtraction "splitting," helping students identify tens-based relationships.
• Independent Practice: Challenging word problems require students to extract data and write complete equations without visual prompts.

This follows a gradual release model, moving from heavy scaffolding to independent application.

Standards Alignment

Primary focus is 1.OA.C.6, requiring students to add and subtract within 20 using strategies like "making ten." Word problems align with 1.OA.A.1 for solving "adding to" and "taking from" situations. Both standard codes can be copied directly into lesson plans, IEP goals, or district curriculum mapping tools.

How to Use It

Use this during a math block after teaching "make-ten" strategies. It works well as a formative assessment; observe students during Part 1 to see if they identify partners of ten correctly. Completion takes roughly 25 minutes. Sections can be separated for use across multiple days.

Who It's For

Designed for first-graders building fluency and second-graders needing strategy refreshers. It is ideal for visual learners who benefit from broken-down equations. Pair with 10-frame counters or number lines for students requiring additional concrete support during the subtraction portions of the worksheet.

Research from Fisher & Frey (2014) highlights scaffolded practice as essential for math fluency when moving from concrete to abstract reasoning. This worksheet applies those principles by teaching "making 10," a critical bridge for addition and subtraction within 20. By providing prompts for number decomposition, the resource reduces executive function demands, letting learners focus on operational relationships rather than simple computation. NAEP data shows that mastering these decomposition strategies in first grade leads to significantly higher proficiency in multi-digit arithmetic and algebraic reasoning in later years. The word problems reinforce standard 1.OA.C.6 by situating numbers in relatable contexts, ensuring students understand the functional utility of math rather than just memorizing facts. This evidence-based approach supports long-term retention of core mathematical concepts, fosters a growth mindset through successful self-assessment, and prepares students for more complex multi-step problem solving in future units.