Maryland Math 1.NOS.D.9.a
The Standard
- 1.NOS.D.9
- Recall or quickly derive addition and subtraction facts within 20.
Use the count on and count back strategies to add and subtract (e.g., 4 + 1, 7 – 2, etc.).
Maryland College and Career Ready Standards for Mathematics (2025) · ADD AND SUBTRACT WITHIN 20.
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students start at a number and count forward to add. They count backward to subtract. They take one counting step for each number added or subtracted.
What Mastery Looks Like
- For 9 + 3, a student says 10, 11, 12 and answers 12. For 14 − 2, they say 13, 12 and answer 12.
Common Misconceptions
- Some students count the starting number as their first step, so they get an answer that is off by one. Others count forward when subtracting or count every object from one instead of starting at the given number.
How to Assess It
- Ask students to solve 8 + 3 and 12 − 2. Have them draw each jump on a 0 to 20 number path and write both answers.
Lesson moves
Ways to Teach It
Put a counter on 8 on a 0 to 20 number path; move three spaces right, then start again and move two spaces left.
Ask, "For 7 + 2, why is 8 the first number you say?" Have students explain to a partner.
Flip cards numbered 5 to 15 and 1 to 4; race to show their sum and difference with counted jumps.
Set out 12 pencils, give away 3, and count back from 12 to tell how many remain.
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Printable 1.NOS.D.9.a Worksheet
A ready-to-print activity worksheet aligned to 1.NOS.D.9.a, with an answer key for the teacher on its own page. No account needed.
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Related Standards
- 2.NOS.C.8.a
Use strategies based on counting (e.g., counting on, counting back) and place value (e.g., partial sums, making tens, etc.) to add and subtract.
- 1.NOS.E.12.b
Use counting strategies, properties of operations, and/or the inverse relationship between addition and subtraction to subtract.
- 2.NOS.B.6.a
Use counting, make ten, and ten more/less, doubling strategies to add and subtract.
- 1.NOS.E.13.b
Use counting strategies, properties of operations, and/or the inverse relationship between addition and subtraction to subtract.
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