This page makes free printable adding 3 numbers worksheets on demand: press the button and you get a new sheet of 20 problems with a matching answer key, ready for US Letter or A4 paper. The version loaded below opens with items in the shape of 5 + 4 + 6 and 2 + 1 + 7; the key lists 15 and 10 next to their question numbers.
‘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 problems here use three single-digit numbers at a time, which keeps the arithmetic honest without turning the page into a copying exercise. 5 + 4 + 6 and 2 + 1 + 7 are typical of the range.
Written addition is worth practising in columns — which is what these adding 3 numbers worksheets ask for — even when a child working at this level can do it mentally, because the column layout is what makes four-digit work manageable later. A problem such as 3 + 6 + 9 is small enough to do mentally and worth writing out anyway.
Fluency in addition is usually described in two parts: knowing the single-digit facts by recall, and applying a written method to bigger numbers. This sheet exercises whichever of the two the number range implies — for 5 + 4 + 6 the answer 15 should come from memory, not from counting.
Because the addends are regenerated every time, a child cannot learn the sheet instead of the skill. Yesterday's page may have asked for 3 + 5 + 7; today's asks something else in the same shape.
Work of this kind is commonly aligned with the addition strand of most US state standards for this grade; schools outside the US meet the same skill at roughly the same age, which is why these adding 3 numbers worksheets travel well.
| # | Problem | Answer | What to check |
|---|---|---|---|
| 1 | 5 + 4 + 6 = | 15 | Watch for: adding right to left, then reading left to right |
| 2 | 2 + 1 + 7 = | 10 | Check: forgetting the carried digit |
| 3 | 3 + 5 + 7 = | 15 | Look at: treating a longer number as a bigger one |
| 4 | 3 + 6 + 9 = | 18 | Ask about: losing the place columns |
| 5 | 6 + 4 + 2 = | 12 | Watch for: guessing on the near-tens |
| 6 | 4 + 3 + 5 = | 12 | Check: counting on from the wrong number |
A good first problem to do together is 5 + 4 + 6, which comes out at 15. Do 5 + 4 + 6 once with the child narrating, then hand over the pencil and start the clock on the other 20 problems.
Take the first problem on the sheet as it stands, 5 + 4 + 6. Work 5 + 4 + 6 out on paper rather than in your head the first few times, say each step aloud, and check the result against 15 on the key before moving on.
Keys are produced by the same code that produces the questions, so a mismatch between question and answer is not possible on these sheets.
The answer key is generated with the worksheet, not written by hand, so it always matches the sheet in front of you — 5 + 4 + 6 is listed as 15, 2 + 1 + 7 as 10, 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 adding 3 numbers worksheets; the font stays the same size and the spacing opens up.
Keep the finished adding 3 numbers 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