1st Grade Math · Missing Numbers Within 20
Mixed equations Worksheets
Fresh practice, ready to print. Answer key included.
Addition and subtraction equations with one number missing.
Make it yours
Or start with a ready-made version.
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.
- Mixed equations Worksheets, version 1Worksheet PDFAnswer key PDF
- Mixed equations Worksheets, version 2Worksheet PDFAnswer key PDF
- Mixed equations 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.