If you need missing factor worksheets that you can print right now, this page builds them for you — 20 fresh problems, an answer key underneath, and no account to create first. Two of the problems on the sheet as it stands are □ × 12 = 120 and □ × 2 = 20 — answers 10 and 10 — 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.
The sheet mixes the position of the missing value, so the box sometimes sits in the first slot and sometimes in the answer slot. Children who have only met one arrangement usually stall on the other.
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 10 when the same fact is presented backwards.
The sheet uses facts to 12 with one factor hidden, so the difficulty is the reasoning, not the arithmetic.
A missing-number problem such as □ × 12 = 120 asks the child to work backwards, and that is a genuinely different skill from computing forwards. The answer 10 cannot be reached by reading left to right and doing what the sign says.
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 missing factor worksheets travel well.
| # | Problem | Answer | What to check |
|---|---|---|---|
| 1 | □ × 12 = 120 | 10 | Watch for: treating the equals sign as 'the answer comes next' |
| 2 | □ × 2 = 20 | 10 | Check: guess-and-check without adjusting |
| 3 | 2 × □ = 4 | 2 | Look at: using the same operation instead of the inverse |
| 4 | 8 × □ = 24 | 3 | Ask about: ignoring the box and computing the two visible numbers |
| 5 | □ × 2 = 8 | 4 | Watch for: writing the whole equation as the answer |
| 6 | □ × 9 = 72 | 8 | Check: freezing when the box is first |
A good first problem to do together is □ × 12 = 120, which comes out at 10. Do □ × 12 = 120 once with the child narrating, then hand over the pencil and start the clock on the other 20 problems.
The item □ × 2 = 20 is worth doing slowly. The answer to □ × 2 = 20 is 10, 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.
Answers appear next to their question numbers, so a wrong item like □ × 2 = 20 can be found in the key in a second and re-worked while it is still fresh.
Every generated sheet carries its own key on a separate printed page, which lets a child self-mark without seeing the answers while they work.
For a class set, print one sheet, press the new-worksheet button and print again. Each child gets different numbers on the same skill, so nobody can copy the answer to □ × 12 = 120 from a neighbour.
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.
When these become easy, move along the related links below rather than adding more problems to the same sheet.
→ 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