Maryland Math 3.NOS.D.7.a
The Standard
- 3.NOS.D.7
- Fluently add and subtract within 1,000.
Use computational strategies efficiently (e.g., decomposition, partials sums, compensation, make ten/hundred/thousand) to add and subtract.
Maryland College and Career Ready Standards for Mathematics (2025) · USE PLACE VALUE UNDERSTANDING AND PROPERTIES OF OPERATIONS TO PERFORM MULTI-DIGIT ARITHMETIC.
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students add and subtract multi-digit numbers by breaking them into place values or adjusting a number to make the calculation easier. They show their steps and explain how each step affects the answer.
What Mastery Looks Like
- A student can add 368 + 257 with partial sums to get 625. For 602 - 198, they can subtract 200, then add 2 back to get 404.
Common Misconceptions
- Students may add each place separately but forget to trade 10 ones for a ten. When they subtract 200 instead of 198, they may subtract 2 more rather than add 2 back.
How to Assess It
- Exit ticket: Solve 368 + 257 and 602 - 198 using a break-apart or adjustment strategy. Show where you accounted for the extra ten or the 2.
Lesson moves
Ways to Teach It
Give pairs base-ten blocks to build 368 and 257, combine matching places, and trade 10 ones for a ten and 10 tens for a hundred.
Ask, “Why does 602 - 200 + 2 give the same answer as 602 - 198?” Have students explain to a partner.
Give pairs cards with three-digit addition and subtraction problems; have them pick a useful friendly number and show their steps.
Tell students a class collected 368 cans Monday and 257 Tuesday; ask them to find the two-day total using partial sums.
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Printable 3.NOS.D.7.a Worksheet
A ready-to-print activity worksheet aligned to 3.NOS.D.7.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.
- 5.NOS.B.4.b
Use computational strategies (e.g., partial products, doubling and halving) efficiently to multiply.
- 4.NOS.B.3.b
Use computational strategies (e.g., decomposition, partials sums) efficiently.
- 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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