Study Guide — 1.OA.D.8
Determine the unknown whole number in an addition or subtraction equa…
Add and subtract within the grade-level range using strategies and models.
What this standard means
- Determine the unknown whole number in an addition or subtraction equation relating three whole numbers. For example, determine the unknown number that makes the equation true in each of the equations 8 + ? = 11, 5 = _ - 3, 6 + 6 = _.
- Apply determine the unknown whole number in an addition or subtraction equa… with models and explanation
- Adds and subtracts accurately in range
_See printable PDF for diagram._
How to use the 20 practice sets
| Sets | When to use | | --- | --- | | 1–5 | Intro — explore together, short written items | | 6–10 | Core skills — diagrams and written practice | | 11–15 | Mixed review — explain thinking | | 16–20 | Stretch — word problems and mastery tasks |
Pacing: 10–15 minutes per session.
How to practice
1. Draw number bonds or number lines 2. Relate addition and subtraction as inverse operations 3. Check subtraction with addition
_See printable PDF for diagram._
Common mistakes
- Subtracting the smaller from the larger digit regardless of place
Review and practice tests
1. Start Review 1/10 when sets 1–3 feel comfortable. 2. Move up one review level with little help. 3. Use Practice Test 4/10–6/10 for mid-standard checks. 4. Practice Test 10/10 is the mastery bar for 1.OA.D.8.
- [ ] Adds and subtracts accurately in range
- [ ] Uses a model or strategy
- [ ] Checks answers when possible
Materials for this standard
- Practice Problems — 20 printable sets
- Review — 10 difficulty levels
- Practice Test — 10 difficulty levels
- Answer key — for parents and tutors