← Back to Missing Addends

Missing Addends - Worksheet 8 - 1st Grade

Hard

Find the missing number in addition equations (Hard)

23 problems · 10-15 minutes · Skills: addition, algebraic thinking

About This Worksheet

This hard-level worksheet contains 23 problems designed for 1st Grade students practicing missing addends. Hard worksheets feature challenging problems including multi-step questions, missing values, and real-world applications to push students further.

Missing addend problems introduce algebraic thinking — finding an unknown value. This prepares students for equation solving in later grades.

  • Find the missing number in an addition equation
  • Use subtraction to solve for unknowns
  • Build early algebraic thinking skills
  • Represent the unknown with a box or blank to solve
  • Connect missing-addend problems to related subtraction facts

How to Solve: Worked Example

Example Problem: ___ + 8 = 17
Solution Steps:
  1. The missing number is on the left side.
  2. Use subtraction: 17 − 8 = 9.
  3. Check: 9 + 8 = 17. Correct!
Answer: 9
Tip: It doesn't matter which side the blank is on — always subtract the known part from the total.
1
8 + ___ = 12
2
3 + ___ = 16
3
___ + 8 = 17
4
8 + ___ = 13
5
11 + ___ = 19
6
11 + ___ = 14
7
___ + 12 = 18
8
8 + ___ = 16
9
8 + ___ = 19
10
___ + 3 = 15
11
3 + ___ = 20
12
___ + 11 = 20
13
5 + ___ = 16
14
___ + 7 = 20
15
___ + 4 = 14
16
9 + ___ = 16
17
14 + ___ = 19
18
___ + 3 = 16
19
5 + ___ = 16
20
___ + 12 = 16
21
___ + 9 = 12
22
12 + ___ = 15
23
10 + ___ = 19

Answer Key

1. 42. 133. 94. 55. 86. 37. 68. 89. 1110. 1211. 1712. 913. 1114. 1315. 1016. 717. 518. 1319. 1120. 421. 322. 323. 9

Frequently Asked Questions

How do I download this missing addends - worksheet 8 worksheet?

Click the "Download PDF / Print" button at the top of the worksheet. You can save it as a PDF or print it directly. The answer key will be on a separate page.

How do I find worksheets at different difficulty levels?

Each subtopic has 10 worksheets: Worksheets 1-3 are Easy, 4-7 are Medium, and 8-10 are Hard. Start with Easy worksheets to build confidence, then progress to harder ones.

What skills does this addition worksheet cover?

This worksheet focuses on addition, algebraic thinking. It is designed for 1st Grade students and provides structured practice through varied problem types with a worked example to guide students before they begin.

Can I use this worksheet in my classroom?

Yes. All worksheets on K12Worksheets are free for classroom use. You can print copies for your entire class. With 10 worksheets per subtopic at three difficulty levels, you have plenty of options for differentiated instruction and individualized practice.

How many problems are on this worksheet?

This worksheet contains 23 problems. It typically takes 10-15 minutes to complete. An answer key with all solutions is included so parents and teachers can check work quickly.