1.OA.C.6 — Add and Subtract Within 20

What 1.OA.C.6 Covers

Grade 1 students add and subtract within 20 using strategies such as counting on, making a ten, and using the relationship between addition and subtraction — while also reaching true fluency (instant recall) for the smaller facts within 10. It's a two-part goal: strategy-based problem solving for the full 20-range, memorized speed for the 10-range.

Where It Fits

Builds directly on K.OA.A.5, where facts within 5 became automatic. By Grade 2, the fluency bar for this same 20-range moves from "can use a strategy" to "knows from memory" — see 2.OA.B.2.

Common Mistakes

• Counting all from 1 instead of counting on from the larger addend (e.g., solving 8 + 5 by counting 1-2-3...13 rather than 9,10,11,12,13).
• Not using "make a ten" for facts like 9 + 6 (9 + 1 + 5), which is faster and less error-prone than counting.
• Treating addition and subtraction facts as unrelated instead of using known sums to solve differences (8 + 5 = 13, so 13 − 5 = 8).

⚙️ 1.OA.C.6 Practice Worksheet Generator

Numbers are locked to this standard's range (within 20) so every problem matches 1.OA.C.6 exactly.

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