K5Print Free printable worksheets for K–5

10 printable sets · answer key on every set

Number Bonds to 20 Worksheets

  • CCSS 1.OA.B.3
  • 20 problems per set
  • Answer key included

What this skill is

Pairs that make each number up to 20.

When it comes up: Throughout first grade.

The mistake to watch for

Knowing bonds to 10 solidly but starting over from scratch for the teens, rather than using 10 as a landmark.

How to help

Ask "how far to ten, then how much more?" every time. The bonds to 10 already known do most of the work.

Next: Missing addend problems.

A worked example

What goes with 13 to make 20? Count up from 13 to 20: that is 7 steps. You can also see it with tens: 3 + 7 = 10, so 13 + 7 = 20.

Words to know

part
One piece of a whole. In 3 + 4 = 7, the parts are 3 and 4.
whole
All of something. In 3 + 4 = 7, the whole is 7.
total
All of the things added together.
pair
Two things that go together.
twenty
The number 20, two tens.

Practice

Write the missing part.

Showing Set 1 · 20 problems

  1. ___ + 8 = 20
  2. ___ + 4 = 20
  3. ___ + 3 = 20
  4. ___ + 17 = 20
  5. ___ + 18 = 20
  6. ___ + 15 = 20
  7. ___ + 16 = 20
  8. ___ + 1 = 20
  9. ___ + 20 = 20
  10. ___ + 14 = 20
  11. ___ + 19 = 20
  12. ___ + 11 = 20
  13. ___ + 7 = 20
  14. ___ + 2 = 20
  15. ___ + 0 = 20
  16. ___ + 12 = 20
  17. ___ + 5 = 20
  18. ___ + 9 = 20
  19. ___ + 13 = 20
  20. ___ + 6 = 20

Download this set20 problems · answer key included PDF

Answer key
  1. 12
  2. 16
  3. 17
  4. 3
  5. 2
  6. 5
  7. 4
  8. 19
  9. 0
  10. 6
  11. 1
  12. 9
  13. 13
  14. 18
  15. 20
  16. 8
  17. 15
  18. 11
  19. 7
  20. 14

All 10 sets

Each set is a different list of 20 problems with its own answer key. Use the buttons above to look at one on this page, or download any of them as a PDF.

How these sheets were made
  • Problems are generated for each set and checked against 1.OA.B.3 before the sheet is built — no duplicates, and every problem falls inside the standard's number range.

Common Core State Standards © 2010 National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.