1.NOS.D: Add and subtract within 20.

Add and subtract within 20.

1.NOS.D.9Recall or quickly derive addition and subtraction facts within 20. a. Use the count on and count back strategies to add and subtract (e.g., 4 + 1, 7 – 2, etc.). b. Use the make ten strategy to add and subtract with combinations of 10 (e.g., 7 + 3, 6 + 4, 10 – 3, 10 – 6, etc.). c. Use the ten more and ten less strategies to add and subtract (including those with a difference of 10). d. Use the doubles to add and subtract (e.g., 6 + 6 = 12, 14 – 7 = 7, etc.)

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