Subtraction as an Unknown Addend Worksheets for 1st Grade
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Prints on one US Letter page; the answer key is a separate page. Print at 100% / "Actual size" on US Letter paper. Free for personal and classroom use. Version 1 of 10. Choose another version.
Skill: Solving subtraction facts by finding the missing number in a related addition fact
Teaching tips and what to try next
Made for first graders who know addition facts within 10 better than subtraction facts. If your child counts backward and keeps landing one off, show counting up from the smaller number instead, which matches the "think addition" step. Build the same skill with smaller numbers in Missing Addends Within 10, then see the full set of related facts in Fact Families Within 20.
10 versions, each with its own answer key
Same skill and layout, a fresh set of problems in every version, so children can keep practicing without repeating a page. Problems are not repeated between versions unless a skill has only a small number of possible problems (for example, the addition facts within 10).
- Version 1: Sheet · Key · Both
- Version 2: Sheet · Key · Both
- Version 3: Sheet · Key · Both
- Version 4: Sheet · Key · Both
- Version 5: Sheet · Key · Both
- Version 6: Sheet · Key · Both
- Version 7: Sheet · Key · Both
- Version 8: Sheet · Key · Both
- Version 9: Sheet · Key · Both
- Version 10: Sheet · Key · Both
Download all 10 versions (one PDF)All 10 answer keys (PDF)
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About this worksheet
Many children find subtraction harder than addition. A helpful strategy is to turn subtraction into an addition question: to solve 13 – 5, ask "5 plus what makes 13?" First graders are expected to understand subtraction as an unknown addend problem, and this first grade worksheet builds the habit of thinking addition to subtract.
The page has twelve rows. Each row first asks a missing addend question, such as 5 + ___ = 13, and then asks for the matching subtraction fact, 13 – 5 = ___. Because the two answers are the same, children see that the facts are connected rather than separate things to memorize. The numbers being added are from 2 to 10, so the totals go up to 20. Each of the ten versions has new facts and its own answer key.
How to use it: work the first row together and say it out loud: "5 and how many more make 13? 8. So 13 take away 5 is 8." Counting on from the smaller number with fingers or a number line is a fine way to find the missing part at first. Over time, encourage known facts, such as doubles and making ten. If both answers in a row do not match, that is a quick signal to check the work.
The answer key shows both answers in every row. For more missing number practice, try our Missing Addends Within 10 worksheet and our Missing Addends Within 20 worksheet. To see all four related facts at once, try our Fact Families Within 20 worksheet.