Maryland Math 3.NOS.D.7.c
The Standard
- 3.NOS.D.7
- Fluently add and subtract within 1,000.
Determine and explain when a strategy is most efficient.
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 compare ways to add and subtract three-digit numbers. They choose a method that fits the numbers and explain why it takes fewer or simpler steps.
What Mastery Looks Like
- For 398 + 205, a student moves 2 from 205 to 398, then adds 400 + 203. For 600 − 298, they count up from 298 and explain why that avoids several regrouping steps.
Common Misconceptions
- Students may round 398 to 400 but forget to adjust for the extra 2. Some use the same method for every problem, even when the numbers make another method simpler.
How to Assess It
- Exit ticket: Solve 398 + 205 and 467 + 386. Name the method you chose for each and explain why it fits those numbers.
Lesson moves
Ways to Teach It
Build 398 and 205 with base-ten blocks, move two ones to make 400, then compare that method with adding by place value.
Ask: For 600 − 298, would you count up or regroup? Show both methods and explain which you would use again.
Deal six digit cards to build two three-digit addends; partners solve and explain why their chosen method fits the numbers.
Give students a school supply order for 398 pencils and 205 more pencils; ask for the total and why making 400 helps.
Free download
Printable 3.NOS.D.7.c Worksheet
A ready-to-print activity worksheet aligned to 3.NOS.D.7.c, with an answer key for the teacher on its own page. No account needed.
PDF, US Letter, prints cleanly in black and white.
Download the worksheetKeep exploring
Related Standards
- 6.NOS.B.3.d
Determine and explain when a strategy or algorithm is most efficient.
- 4.NOS.B.3.d
Determine and explain when a strategy or algorithm is most efficient.
- 5.NOS.B.4.d
Determine and explain when a strategy or algorithm is most efficient.
- 2.NOS.C.8.c
Determine and explain when a strategy is most efficient.
Turn this exact standard into a lesson
Grade, subject, topic, and the complete standard are prefilled. Create one free, no account needed.
Also for this standard:Make a WorksheetMake a QuizMake a Sub Lesson