Maryland Math 2.NOS.C.9.c
The Standard
- 2.NOS.C.9
- Add and subtract within 1000, recognizing that when adding or subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.
Use properties of operations, and/or the relationship between addition and subtraction to add and subtract.
Maryland College and Career Ready Standards for Mathematics (2025) · USE REPRESENTATIONS, PLACE VALUE UNDERSTANDING, AND PROPERTIES OF OPERATIONS TO ADD AND SUBTRACT.
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students rearrange or break apart numbers to make addition easier. They use addition facts to solve subtraction problems.
What Mastery Looks Like
- A student can solve 8 + 7 by making 10 + 5 and explain why the total stays 15. They can solve 15 - 7 by thinking 7 + 8 = 15.
Common Misconceptions
- Some students switch numbers in subtraction as if it works like addition. Others do not see how an addition fact can help them subtract.
How to Assess It
- Ask students to solve 16 - 9 using an addition fact. Have them write the fact and explain how it gives their answer.
Lesson moves
Ways to Teach It
Give pairs linking cubes to build 8 + 7, then move two cubes to make 10 + 5.
Ask, 'Why does 7 + 9 equal 9 + 7, but 16 - 7 does not equal 16 - 9?'
Give pairs the numbers 7, 9, and 16; have them race to write two addition facts and two subtraction facts.
Put 18 pencils in a cup, remove 7, and ask students to use 7 + ? = 18 to find how many remain.
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Printable 2.NOS.C.9.c Worksheet
A ready-to-print activity worksheet aligned to 2.NOS.C.9.c, with an answer key for the teacher on its own page. No account needed.
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Related Standards
- 1.NOS.E.10.c
Use properties of operations, and/or the inverse relationship between addition and subtraction to add.
- 2.NOS.C.8.b
Use properties of operations, and the inverse relationship between addition and subtraction 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.
- 3.NOS.D.7.b
Use properties of operations, and/or the inverse relationship between addition and subtraction.
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