1st Grade Missing Numbers Within 20 Worksheets
Fresh practice, ready to print. Answer key included.
Addition and subtraction equations within 20 with one number missing. Children find a missing addend, then a missing number in a subtraction equation, and finally a mix of both.
Make it yours
Or start with a ready-made version.
What's on the worksheet
- Missing addend
Equations such as 8 + ____ = 11 and ____ + 6 = 14.
- Missing number in subtraction
Equations such as 13 − ____ = 5 and ____ − 4 = 9.
- Mixed equations
Addition and subtraction equations with one number missing.
How it works: a quick refresher
The rules this worksheet practices, then one problem worked from start to finish.
| Strategy | How it works |
|---|---|
| A missing addend is a count-on | For 8 + ____ = 11, count from 8 up to 11: 9, 10, 11. That is 3. |
| The blank can be on either side of the plus | ____ + 6 = 14 and 6 + ____ = 14 both ask for 8. |
| A missing number taken away | For 13 − ____ = 5, ask 13 − 5. The number taken away is 8. |
| A missing starting number | For ____ − 4 = 9, add the two numbers you can see: 4 + 9 = 13. |
| Check by using the sign | Put the answer in the blank and work the problem. Both sides should match. |
Worked example
Find the missing number: 8 + ____ = 11.
- 1Count on from 8 to 11: 9, 10, 11.
- 2That is 3 counts, so the missing number is 3.
- 3Check: 8 + 3 = 11.
Ready-made versions
Three fixed versions you can link to or share. Each is a PDF with its own answer key.
- 1st Grade Missing Numbers Within 20 Worksheets, version 1Worksheet PDFAnswer key PDF
- 1st Grade Missing Numbers Within 20 Worksheets, version 2Worksheet PDFAnswer key PDF
- 1st Grade Missing Numbers Within 20 Worksheets, version 3Worksheet PDFAnswer key PDF
Grade level and standard
Written for 1st grade math (operations) and aligned to CCSS 1.OA.D.8. It also works as review in later grades.
Common questions
- Is there an answer key?
- Yes. Every worksheet has a matching answer key with each answer worked on the same grid or layout as the question. The worksheet ID printed at the bottom of each page pairs a sheet with its key.
- Should my child write the whole equation or only the missing number?
- Only the missing number. The rest of the equation is already printed.
- Are the answers ever bigger than 20?
- No. Every number in the equation, including the one that was missing, is from 2 to 20.
- How many different versions are there?
- About a million per skill. Each time you press the button the problems are generated fresh, so you can print a different version for every student, a retake, or another night of practice.
- Are the worksheets free?
- Yes. They are free to print and copy for your home or classroom, with no sign-up.