10 printable sets · answer key on every set

Missing Addend Worksheets

CCSS 1.OA.D.8
20 problems per set
Answer key included

What this skill is

Finding the unknown part when the total and one part are given: 7 + ___ = 12.

When it comes up: Second half of first grade.

The mistake to watch for

Adding the two visible numbers, answering 19 for 7 + ___ = 12. The equals sign is read as "the answer comes next" rather than "the same amount".

How to help

Cover the total with your hand and ask what is missing, not what to add. Balance scales help — both sides must match.

Next: Fact families.

A worked example

Try 6 + ___ = 11. Start at 6 and count up to 11: 7, 8, 9, 10, 11. That is 5 steps, so the missing number is 5.

Words to know

add: To put numbers together to find how many in all.
sum: The answer you get when you add.
total: All of the things added together.
equal: The same amount. The sign = means "is equal to".
missing: Not there yet. A missing number is the one you need to find.

Practice

Write the missing number.

Showing Set 1 · 20 problems

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

Download this set20 problems · answer key included PDF

Answer key

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.D.8 before the sheet is built — no duplicates, and every problem falls inside the standard's number range.