Addition Within 20
Skill: Adding two numbers with sums from 11 to 20
Download PDF worksheetAnswer key (PDF)
Free for personal and classroom use. Print at 100% / "Actual size" on US Letter paper.
About this worksheet
After children master sums up to 10, the next challenge is adding across ten, such as 8 + 5 or 9 + 7. This first-grade worksheet gives 24 vertical addition problems where every sum is between 11 and 20, and both numbers being added are from 2 to 10. These are the facts that first graders most often find tricky, so focused practice here makes a big difference.
How to use it: the most helpful strategy is "make a ten." For 8 + 5, think: 8 needs 2 more to make 10, so take 2 from the 5. Now the problem is 10 + 3, which is 13. Doubles and near doubles are another useful tool; if your child knows 6 + 6 = 12, then 6 + 7 is just one more, 13. Ten-frames, counters, or a number line from 0 to 20 can help children see what is happening. Counting on from the larger number is fine while children are learning, but encourage them to try a strategy that uses ten as they gain confidence.
The answer key on the second page lists every sum in order. When your child misses a fact, model it with objects and talk through a make-ten strategy together. A few minutes of practice on several days will build fluency more than one long session. This worksheet supports Common Core standard 1.OA.C.6 (add and subtract within 20, using strategies such as counting on, making ten, and using known sums).
Count and Trace Numbers 1-10
Addition Within 10
Subtraction Within 10