Missing Numbers in Subtraction Within 20 Worksheets for 1st Grade

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Grade 1MathAddition & SubtractionCCSS 1.OA.D.8

Skill: Finding the unknown number in a subtraction equation within 20

Preview of the Missing Numbers in Subtraction Within 20 printable worksheet
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Teaching tips and what to try next

This suits first graders who already know most subtraction facts within 20 and are ready to think about where the unknown can sit. The blank at the start trips children up most, because they try to subtract the two numbers they can see. Warm up with Missing Addends Within 10, or link the facts together 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).

Download all 10 versions (one PDF)All 10 answer keys (PDF)

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About this worksheet

First graders are asked to find an unknown number in any spot of an equation, not just after the equal sign. This first-grade worksheet gives twenty subtraction equations with one number missing, such as 14 – ___ = 6 or ___ – 3 = 9, so children practice thinking about how the three numbers in a subtraction fact fit together.

Half of the blanks are in the middle, where children find the number being taken away, and half are at the start, where they find the number we started with. Every equation stays within 20, the numbers taken away are 10 or less, and no equation appears twice on the same page. Many problems start with a teen number, so children practice the facts that cross ten, which are the hardest ones to remember. Each of the ten versions has new equations.

How to use it: teach your child to turn each problem into an addition question. For 14 – ___ = 6, ask, "6 plus what makes 14?" For ___ – 3 = 9, ask, "What is 9 plus 3?" Counting up on a number line or with fingers works well for the middle blanks. Once a blank is filled in, have your child read the whole equation out loud to check that it is true. If the first column feels hard, try a few with small counters first.

The answer key shows every equation with the missing number filled in. This worksheet supports Common Core standard 1.OA.D.8. For more practice, try our Missing Addends Within 10 worksheet and our Subtraction Within 20 worksheet.