3rd Grade Mental Addition and Subtraction Strategies Worksheet — Level 1 — Practice Set 3 — Answers
Answer sheet with worked solutions for the 3rd Grade addition worksheet.
Success TutoringWorksheetsAnswer sheet3rd Grade · Mathematics · Addition3rd Grade Mental Addition and Subtraction Strategies Worksheet — Level 1 — Practice Set 3 — Answers
Fill in each step of the strategy, then write the answer.
1.8 + 7 = 8 + 2 + (answer space) = (answer space)
Answer: 5, 15
- 8 + 2 = 10 (a ten)
- 10 + 5 = 15
2.9 + 8 = 9 + 1 + (answer space) = (answer space)
Answer: 7, 17
- 9 + 1 = 10 (a ten)
- 10 + 7 = 17
3.10 + 9 = (answer space) + (answer space) + 1 = (answer space)
Answer: 9, 9, 19
- Double 9 is 18
- 18 + 1 = 19
4.6 + 7 = 6 + 4 + (answer space) = (answer space)
Answer: 3, 13
- 6 + 4 = 10 (a ten)
- 10 + 3 = 13
5.7 + 5 = 7 + 3 + (answer space) = (answer space)
Answer: 2, 12
- 7 + 3 = 10 (a ten)
- 10 + 2 = 12
6.4 + 5 = (answer space) + (answer space) + 1 = (answer space)
Answer: 4, 4, 9
- Double 4 is 8
- 8 + 1 = 9
7.7 + 8 = 7 + 3 + (answer space) = (answer space)
Answer: 5, 15
- 7 + 3 = 10 (a ten)
- 10 + 5 = 15
8.7 + 6 = 7 + 3 + (answer space) = (answer space)
Answer: 3, 13
- 7 + 3 = 10 (a ten)
- 10 + 3 = 13
9.9 + 8 = (answer space) + (answer space) + 1 = (answer space)
Answer: 8, 8, 17
- Double 8 is 16
- 16 + 1 = 17
10.9 + 4 = 9 + 1 + (answer space) = (answer space)
Answer: 3, 13
- 9 + 1 = 10 (a ten)
- 10 + 3 = 13
11.9 + 7 = 9 + 1 + (answer space) = (answer space)
Answer: 6, 16
- 9 + 1 = 10 (a ten)
- 10 + 6 = 16
12.7 + 8 = (answer space) + (answer space) + 1 = (answer space)
Answer: 7, 7, 15
- Double 7 is 14
- 14 + 1 = 15
Marking tips
- Give credit for correct method even when the final answer slips — the working shows where the thinking went right.
- For open-ended tasks, use the success criteria as a checklist rather than looking for one "right" answer.
- Celebrate what went well first, then pick one thing to work on next.