Worksheet BenchK–5 practice for adults supporting learners
Computation practice

Missing Addends Within 20 Worksheets for 1st Grade

These missing addends within 20 worksheets give parents and teachers focused, repeatable practice for 1st Grade learners. Find an unknown addend in an addition or subtraction equation within 20. Choose a fixed-seed sample or make a fresh printable without creating an account.

Customize & downloadSee free samples

Opens a reproducible 20-question sample in the builder. Adjust it if needed, then choose the worksheet and answer-key PDF package.

Reproducible fixed seeds

Three free worksheet samples

Preview a fixed sample here. Opening one takes that exact seed into the builder, where you can inspect all 20 questions, adjust the settings, and choose a PDF package.

  1. Proof 01 of 03Fixed seed
    Missing Addends Within 20
    Seed leaf-16-1-missing-addends-within-20-sample-a7
    1. Find the missing addend: 0 + ___ = 3
    2. Find the missing addend: ___ + 18 = 20
    3. Find the missing addend: ___ + 12 = 14
    4. Find the missing addend: 1 + ___ = 2

    This opens the same 20-question seed in the builder. Review the full set, adjust it if needed, then choose a printable PDF package.

    Open sample in builder
  2. Proof 02 of 03Fixed seed
    Missing Addends Within 20
    Seed leaf-16-1-missing-addends-within-20-sample-m3
    1. Find the missing addend: 1 + ___ = 6
    2. Find the missing addend: 0 + ___ = 5
    3. Find the missing addend: ___ + 2 = 5
    4. Find the missing addend: ___ + 5 = 9

    This opens the same 20-question seed in the builder. Review the full set, adjust it if needed, then choose a printable PDF package.

    Open sample in builder
  3. Proof 03 of 03Fixed seed
    Missing Addends Within 20
    Seed leaf-16-1-missing-addends-within-20-sample-z9
    1. Find the missing addend: 0 + ___ = 2
    2. Find the missing addend: 8 + ___ = 9
    3. Find the missing addend: 8 + ___ = 15
    4. Find the missing addend: ___ + 7 = 10

    This opens the same 20-question seed in the builder. Review the full set, adjust it if needed, then choose a printable PDF package.

    Open sample in builder

Next step: open a sample in the builder. The fixed seed is preserved until you choose to generate a different set.

Computation routine

Calculate, check, explain.

Combine the quantities and check that the sum is reasonable for the stated range.

  1. 01

    Name the operation and useful number relationships.

  2. 02

    Solve with an efficient written or mental strategy.

  3. 03

    Check the result with the inverse operation or an estimate.

01Problem

Find the missing addend: 0 + ___ = 3

02 · Answer3
03 · Check

Combine the quantities and check that the sum is reasonable for the stated range. This example supports the page objective: Find an unknown addend in an addition or subtraction equation within 20.

Teacher sequence

Introduce, model, practice, inspect

Move through the sequence vertically. Each step has a distinct classroom decision rather than a hidden swipe panel.

  1. Introduce

    Set one visible purpose

    • Encourage a strategy such as making ten, decomposing, or using place value. For this missing addends within 20 set, begin without a timer.
  2. Model

    Demonstrate the calculation strategy

    • Combine the quantities and check that the sum is reasonable for the stated range.
  3. Practice

    Assign the focused set

    • Check a few answers by reversing the operation with subtraction. Regenerate only when the learner is ready for another arrangement of the same objective.
  4. Inspect

    Use errors to choose the next move

    • Losing track of a regrouped ten when working vertically. Watch for this specifically during missing addends within 20 practice.
    • Adding digits from different place-value columns. Use the worked correction as the next teaching example.
Standards reference

Skill alignment

Alignment labels identify the primary skill practiced. A worksheet is supplemental practice and does not assess every part of a standard.

System
Common Core
Standard
1.OA.D.8
Match
primary alignment
Reference
Common Core State Standards Initiative — Mathematics Standards
Planning inspection log

Frequently asked questions

Open a row to inspect the guidance most relevant to this worksheet.

  1. What does this 1st Grade Missing Addends Within 20 worksheet practice?
    Finding

    Find an unknown addend in an addition or subtraction equation within 20.

  2. How should adults use the Missing Addends Within 20 printable?
    Finding

    Start with one untimed set, review the learner's strategy, and use the answer key to discuss errors. Generate a new fixed-seed set only after the current skill is understood.

  3. Does the Missing Addends Within 20 download include answers?
    Finding

    Yes. The free PDF can include an appended answer key, or the answer key can be downloaded separately for adult use.

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Automated QA passedUpdated 2026-07-15

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