Maryland Math 1.NOS.D.9.d
The Standard
- 1.NOS.D.9
- Recall or quickly derive addition and subtraction facts within 20.
Use the doubles to add and subtract (e.g., 6 + 6 = 12, 14 – 7 = 7, 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 find the total when two equal groups are put together. They use the same fact to find what remains when one group is taken away.
What Mastery Looks Like
- A student can show 8 + 8 with two groups and find 16. They can then solve 16 - 8 and explain why 8 remains.
Common Misconceptions
- Some students think doubling 8 means adding 2, not making two groups of 8. Others know 8 + 8 = 16 but do not see how it helps with 16 - 8.
How to Assess It
- Exit ticket: Draw circles to show 7 + 7. Then solve 14 - 7 and write how your drawing helps.
Lesson moves
Ways to Teach It
Give students 14 counters; have them make two equal groups, write 7 + 7 = 14, then remove one group and write 14 - 7 = 7.
Ask partners, 'If 9 + 9 = 18, how can that help you solve 18 - 9?' Have them explain with a sketch.
Play a matching game with cards showing 6 + 6, 12, and 12 - 6; students collect linked sets and explain each match.
Set out 10 pairs of socks; students count 20 socks, then put 10 in a basket and tell how many remain.
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Printable 1.NOS.D.9.d Worksheet
A ready-to-print activity worksheet aligned to 1.NOS.D.9.d, with an answer key for the teacher on its own page. No account needed.
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Related Standards
- 1.NOS.D.9.a
Use the count on and count back strategies to add and subtract (e.g., 4 + 1, 7 – 2, 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.B.6.c
Use the inverse operation to add and subtract (e.g. think of 7 + ? = 15 to solve 15 – 7 = ?).
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