1.NBT.4 — Adding Within 100: Two-Digit & One-Digit Numbers
Practice adding a two-digit number and a one-digit number, or a two-digit number and a multiple of 10, using place-value strategies to find sums within 100.
Solve each addition problem and write the answer on the line.
- 1.23 + 5 =
- 2.41 + 8 =
- 3.30 + 40 =
- 4.56 + 3 =
- 5.20 + 50 =
- 6.74 + 4 =
- 7.60 + 30 =
- 8.15 + 7 =
- 9.43 + 20 =
- 10.82 + 6 =
- 11.50 + 40 =
- 12.67 + 2 =
- 13.34 + 50 =
- 14.11 + 9 =
- 15.25 + 30 =
- 16.48 + 1 =
- 17.70 + 20 =
- 18.53 + 6 =
- 19.62 + 30 =
- 20.37 + 2 =
- 21.44 + 40 =
- 22.91 + 7 =
What this worksheet covers
Twenty-two addition problems fill the page, and the complete key sits behind them in the same PDF. What makes this set particular: two of the twenty-two problems require regrouping and the rest do not, so the two cases are mixed rather than blocked together; numbers reach 91. The whole sheet sits inside Common Core 1.NBT.4, in the grade 1 Number & Operations in Base Ten strand.
Skills practiced
At this point in the sequence, work in addition is really about fact fluency within 20, then addition within 100. Working the page asks a student to regroup past ten rather than counting up one at a time. Consistency across the page matters more than any single answer on it.
How to use this worksheet
Grade 1 attention runs short, so split these twenty-two problems over two or three short sittings rather than pushing through in one. Keep a number line or a ten-frame within reach — reaching for it is a strategy, not a failure. Date the sheet before filing it. A page from six weeks ago is the cheapest evidence you have that something is sticking.
One mistake to watch for
Counting all instead of counting on: for 7 + 3, the student starts at one.
Cardinality has not fully transferred — the student does not yet trust that "seven" names the whole set and can be the starting point.
Hide the first set under a cup, label it with the numeral, and count on from there. When the set cannot be counted, counting on is the only option available.
Related worksheets
More grade 1 addition
Everything else on the site at this exact level — grade 1, addition, same difficulty.
- Adding Up: Grade 1 Word Problems Within 20 — grade 1, 22 problems
- 1.NBT.5 — 10 More or 10 Less Practice — grade 1, 20 problems
- Grade 1 Addition Practice — grade 1, 18 problems
A step either side
The same topic one grade down and one grade up — the easier sheet is often the faster fix when this one is not landing.
- Counting Coins and Bills — Grade 2 Money Practice — grade 2, 22 problems
- 2.NBT.7 — Adding Within 1000 Practice — grade 2, 20 problems
- 2.OA.4 — Rectangular Arrays & Equal Addends Practice — grade 2, 22 problems
- Grade 2 Addition Practice — grade 2, 20 problems
Free to download, free to print, and free to photocopy for a whole class — this addition sheet and its key are one PDF, aimed at fact fluency within 20, then addition within 100.