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Skills Covered

Find missing addends and differences to 20
Apply inverse operations with teen numbers
Build algebraic thinking with larger numbers

Strengthen mental math strategies
Develop problem-solving persistence
Prepare for equation solving

How to Use This Worksheet

Each problem presents a fact family triangle with sums up to 20 and equations with missing values. Students must determine each unknown number, combining fact family knowledge with computation skills for larger numbers.

In the Classroom

This is the most challenging fact family printable in the series. Use for students who have demonstrated fluency with "Write All" formats and "Missing Numbers Within 10." Great for early finishers or enrichment.

At Home

Work through the first problem together. Show your child how to use the triangle numbers to figure out the missing values. If they get stuck, have them try the addition facts first, then use those to help with the subtraction facts.

Tips for Success

Students should master "Within 10 Missing" before attempting this
Encourage students to write the known facts first, then use them to find unknowns
Allow use of manipulatives or a number line as needed
Use the answer key for self-checking

Common Core Standards Alignment

This worksheet supports the following Common Core State Standards for Mathematics:

1.OA.B.4 - Understand subtraction as an unknown-addend problem
1.OA.D.8 - Determine the unknown whole number in an addition or subtraction equation
2.OA.B.2 - Fluently add and subtract within 20 using mental strategies