Mystery Bureau › Grade 1 standards › 1.OA.C.6
📘 Common Core · 1.OA.C.6 · Grade 1
This is the longest standard in first grade for a reason: it names the strategies, not just the outcome. Making ten, decomposing to a ten, and using addition to solve subtraction are all listed explicitly, which means a first grader who gets the right answers by counting one at a time has not yet met it. The problems that cross ten are where all of this is actually tested.
Quoted verbatim from the Common Core State Standards for Mathematics. Nothing here is paraphrased.
| 1.OA.C.6 | Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten; decomposing a number leading to a ten; using the relationship between addition and subtraction; and creating equivalent but easier or known sums. |
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In plain English: Add and subtract within 20, fluently within 10, using strategies like counting on, making ten, and the link between addition and subtraction.
Each one runs in the browser with no account and nothing stored. Five questions apiece.
Real output from the activities above — not written for this page, drawn from the same pools a student gets. The numbers are rebuilt on every attempt.
| 12 + 3 = ? | 15 |
| 6 + 8 = ? | 14 |
| 7 + 3 = ? | 10 |
| 11 − 5 = ? | 6 |
| 20 − 4 = ? | 16 |
| 19 − 5 = ? | 14 |
| Power the reactor to exactly 12 | 12 |
| Power the reactor to exactly 13 | 13 |
| Power the reactor to exactly 14 | 14 |
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