The worksheet generator on this page produces subtraction within 20 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. A typical problem from the sheet in front of you is 12 − 5, which works out to 7; another is 17 − 9, giving 8.
‘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.
This sheet uses minuends from 11 to 18. That is deliberate: wide enough to force real regrouping, narrow enough that a child can still check the answer by adding back.
There are two ways to think about a subtraction such as 12 − 5: taking away, or finding the difference. Children who only know the first find 7 slowly whenever the two numbers are close together.
Every subtraction has an addition hiding inside it, and checking 17 − 9 by adding 8 back to the smaller number is the single most useful habit you can teach on this page.
Subtraction is where arithmetic confidence is usually won or lost. The written method itself is short, but it demands that the child hold a borrowed ten in their head while working on the next column — which is why 12 − 5 can take three times as long as an addition of the same size.
In US classrooms these subtraction within 20 worksheets are commonly aligned with the subtraction strand of most US state standards for this grade, though the exact wording varies from state to state.
| # | Problem | Answer | What to check |
|---|---|---|---|
| 1 | 12 − 5 = | 7 | Watch for: checking by re-subtracting |
| 2 | 17 − 9 = | 8 | Check: borrowing across a zero |
| 3 | 14 − 7 = | 7 | Look at: reading the minus sign as a plus |
| 4 | 11 − 9 = | 2 | Ask about: subtracting the smaller digit from the larger one |
| 5 | 12 − 9 = | 3 | Watch for: forgetting to reduce the column that was borrowed from |
| 6 | 15 − 6 = | 9 | Check: counting back one at a time |
Work 11 − 9 out loud as a demonstration. It gives 2. Children who hear 11 − 9 reasoned through once at the start of a session make noticeably fewer errors in the ten minutes that follow.
A good first problem to do together is 12 − 5, which comes out at 7. Do 12 − 5 once with the child narrating, then hand over the pencil and start the clock on the other 20 problems.
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.
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.
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.
To save these subtraction within 20 worksheets instead of printing them, choose 'Save as PDF' in the printer list. You get the worksheet and the answer key as a single PDF, on Letter or A4 depending on your printer settings.
Keep the finished subtraction within 20 worksheets in date order — the drop in time across ten sheets is the clearest progress report you will get.
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