The worksheet generator on this page produces 1st grade missing addends worksheets with real, freshly randomised numbers — 20 of them per sheet by default — plus the answer key a parent or teacher needs to mark it quickly. The current sheet starts with problems like 3 + □ = 7 and 7 − □ = 6, and the answers (4 and 1) are printed on the key so marking takes about a minute.
‘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.
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 7 − □ = 6 tend to find equations far less strange two or three years later.
The reliable strategy is the inverse operation: to find the box in □ + 6 = 9, undo what is being done. Say that out loud each time until the child says it first.
A missing-number problem such as 3 + □ = 7 asks the child to work backwards, and that is a genuinely different skill from computing forwards. The answer 4 cannot be reached by reading left to right and doing what the sign says.
Missing-number work also exposes memorised facts that are not really known. A child can recite a fact forwards and still be unable to produce 1 when the same fact is presented backwards.
Work of this kind is commonly aligned with the operations and algebraic thinking strand for this grade; schools outside the US meet the same skill at roughly the same age, which is why these 1st grade missing addends worksheets travel well.
| # | Problem | Answer | What to check |
|---|---|---|---|
| 1 | 3 + □ = 7 | 4 | Watch for: freezing when the box is first |
| 2 | 7 − □ = 6 | 1 | Check: treating the equals sign as 'the answer comes next' |
| 3 | □ + 6 = 9 | 3 | Look at: writing the whole equation as the answer |
| 4 | □ − 3 = 4 | 7 | Ask about: using the same operation instead of the inverse |
| 5 | 2 + □ = 11 | 9 | Watch for: ignoring the box and computing the two visible numbers |
| 6 | □ − 1 = 4 | 5 | Check: guess-and-check without adjusting |
Work □ − 3 = 4 out loud as a demonstration. It gives 7. Children who hear □ − 3 = 4 reasoned through once at the start of a session make noticeably fewer errors in the ten minutes that follow.
Try □ + 6 = 9 together before letting the child start alone. The answer to □ + 6 = 9 is 3, and talking through how it was reached takes about a minute and saves several minutes of guessing later in the sheet.
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 4 for 3 + □ = 7.
The answer key is generated with the worksheet, not written by hand, so it always matches the sheet in front of you — 3 + □ = 7 is listed as 4, 7 − □ = 6 as 1, and so on down the page.
Printing works the same on US Letter and A4, because the layout uses relative widths rather than fixed inches. Set margins to default and scaling to 100%, and all 20 problems fit.
If the problems look cramped, drop the count from 20 to a smaller number before printing these 1st grade missing addends worksheets; the font stays the same size and the spacing opens up.
Keep the finished 1st grade missing addends worksheets in date order — the drop in time across ten sheets is the clearest progress report you will get.
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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