Maryland Math 1.NOS.D.9.c
The Standard
- 1.NOS.D.9
- Recall or quickly derive addition and subtraction facts within 20.
Use the ten more and ten less strategies to add and subtract (including those with a difference of 10).
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 add or remove a group of ten without counting every object. They also subtract the ones from a teen number to leave ten.
What Mastery Looks Like
- A student can show 18 as one ten and eight ones. They use that model to solve 8 + 10 = 18, 18 - 10 = 8, and 18 - 8 = 10.
Common Misconceptions
- Some students count every counter instead of using the group of ten. Others answer 17 - 7 = 0 because they forget the ten is still there.
How to Assess It
- Exit ticket: Draw 17 as a full ten-frame and seven loose dots. Use the drawing to solve 7 + 10, 17 - 10, and 17 - 7.
Lesson moves
Ways to Teach It
Give pairs 16 counters and two ten-frames; have them build 16, remove the full ten, rebuild, then remove the six loose counters.
Ask, “Why do 16 - 10 and 16 - 6 have different answers?” Have students draw one ten and six ones to explain.
Deal cards numbered 1 through 9; for a card showing 4, students write 4 + 10 = 14, 14 - 10 = 4, and 14 - 4 = 10.
Show 15 pencils in a bundle of ten and five singles; ask how many remain after giving away the bundle or the singles.
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Printable 1.NOS.D.9.c Worksheet
A ready-to-print activity worksheet aligned to 1.NOS.D.9.c, with an answer key for the teacher on its own page. No account needed.
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Related Standards
- 1.NOS.D.9.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.).
- 2.NOS.B.6.a
Use counting, make ten, and ten more/less, doubling strategies to add and subtract.
- 2.NOS.B.6.b
Use the use ten strategy (e.g., think of 9 + 1 + 6 to solve 9 + 7) and doubles plus one strategy (e.g., think of 4 + 4 + 1 to solve 4 + 5) to add and subtract.
- 2.NOS.C.9.b
Use strategies based on place value (counting on, partial sums, making tens, etc.) to add and subtract.
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