Use this page when you want missing addend worksheets in the next thirty seconds: choose how many problems you want, press print, and the answer key comes out on its own page behind the worksheet. Two of the problems on the sheet as it stands are 4 + □ = 9 and 4 + □ = 6 — answers 5 and 2 — and a new set is one click away.
‘New set of problems’ opens the generator in its own tab. There you can change the problem count and turn the answer key on or off. ‘Print or save as PDF’ opens the print dialog — choose Save as PDF in the printer list to keep the file. The sheet fits US Letter and A4, and the answer key prints on its own page.
A missing-number problem such as 4 + □ = 9 asks the child to work backwards, and that is a genuinely different skill from computing forwards. The answer 5 cannot be reached by reading left to right and doing what the sign says.
The sheet uses single-digit facts with one number hidden, so the difficulty is the reasoning, not the arithmetic.
The reliable strategy is the inverse operation: to find the box in 2 + □ = 8, undo what is being done. Say that out loud each time until the child says it first.
These problems are the first real algebra a child meets. The empty box is a variable in everything but name, and children who are comfortable with 4 + □ = 6 tend to find equations far less strange two or three years later.
Teachers usually place missing addend worksheets alongside the operations and algebraic thinking strand for this grade, which is where the skill sits in the majority of US state frameworks.
| # | Problem | Answer | What to check |
|---|---|---|---|
| 1 | 4 + □ = 9 | 5 | Watch for: guess-and-check without adjusting |
| 2 | 4 + □ = 6 | 2 | Check: using the same operation instead of the inverse |
| 3 | 2 + □ = 8 | 6 | Look at: writing the whole equation as the answer |
| 4 | □ + 4 = 11 | 7 | Ask about: ignoring the box and computing the two visible numbers |
| 5 | 9 + □ = 12 | 3 | Watch for: freezing when the box is first |
| 6 | 9 + □ = 15 | 6 | Check: treating the equals sign as 'the answer comes next' |
Work □ + 4 = 11 out loud as a demonstration. It gives 7. Children who hear □ + 4 = 11 reasoned through once at the start of a session make noticeably fewer errors in the ten minutes that follow.
The item 4 + □ = 6 is worth doing slowly. The answer to 4 + □ = 6 is 2, and the route to it is the route every other problem on this sheet takes — which is why the sheet has 20 of them rather than one.
The key prints on its own page by default. Uncheck the answer-key box before printing if you would rather keep it back and mark the sheet yourself.
Because the numbers are random, there is no shared answer list to look up: the key printed behind your sheet is the only one that fits it, and it shows 5 for 4 + □ = 9.
Portrait orientation is what the sheet is designed for. Landscape works but wastes about a third of the paper, so leave the orientation alone unless you have a reason.
If the problems look cramped, drop the count from 20 to a smaller number before printing these missing addend worksheets; the font stays the same size and the spacing opens up.
Keep the finished missing addend worksheets in date order — the drop in time across ten sheets is the clearest progress report you will get.
→ Free Missing Number Worksheets
Free printable math worksheets from a working math academy director in Korea. Problems come from our own code, not from a published workbook. Every sheet prints on US Letter or A4 with its answer key. All worksheets · Worksheet generator · Korean site
Last updated: 2026-09-13