Maryland Math 2.NOS.C.8.b
The Standard
- 2.NOS.C.8
- Fluently add and subtract within 100.
Use properties of operations, and the inverse 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 change the order or grouping of numbers in an addition problem to make it easier. They use addition to solve or check subtraction, and subtraction to check addition.
What Mastery Looks Like
- A student solves 27 + 8 + 3 by adding 27 + 3 first. They check 38 - 15 = 23 by showing that 23 + 15 = 38.
Common Misconceptions
- Students may swap numbers in subtraction as they do in addition, thinking 15 - 7 equals 7 - 15. They may drop a number when grouping three numbers or miss how addition can check subtraction.
How to Assess It
- Exit ticket: Solve 27 + 8 + 3 by grouping two numbers first. Then solve 38 - 15 and write an addition equation to check your answer.
Lesson moves
Ways to Teach It
Give pairs 8 red, 2 blue, and 5 green counters; have them group the counters two ways and write both addition equations.
Write 14 - 6 = 8 and 8 + 6 = 14; ask, "How does the second equation check the first?"
Have pairs draw two number cards, write an addition fact, swap the addends, and write the related subtraction facts.
Place 18 books on a shelf, remove 7, and have students write a subtraction equation and an addition check.
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Printable 2.NOS.C.8.b Worksheet
A ready-to-print activity worksheet aligned to 2.NOS.C.8.b, 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.9.c
Use properties of operations, and/or the 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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