Maryland Math 5.NOS.B.6.d
The Standard
- 5.NOS.B.6
- Apply and extend previous understanding of addition and subtraction of whole numbers to add and subtract decimals to hundredths.
Determine and explain when a strategy or algorithm is most efficient.
Maryland College and Career Ready Standards for Mathematics (2025) · PERFORM OPERATIONS ON MULTI-DIGIT WHOLE NUMBERS AND WITH DECIMALS TO HUNDREDTHS.
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students solve whole-number and decimal problems using methods that fit the numbers. They compare mental shortcuts and written algorithms, then explain which method takes fewer steps while staying accurate.
What Mastery Looks Like
- A student spots that 398 + 205 is easy to solve by adding 400 + 205, then subtracting 2. For a less convenient calculation, they can choose a written algorithm and explain why it helps.
Common Misconceptions
- Some students think the written algorithm is always fastest. Others round 398 to 400 but forget to adjust the answer. Some say a method is efficient because they like it, without comparing the work involved.
How to Assess It
- Exit ticket: Solve 6.25 + 3.75 and 6.27 + 3.48. Name the method you used for each and explain why it fit those numbers.
Lesson moves
Ways to Teach It
Use place-value disks to solve 3.75 + 2.25, then solve it mentally and compare the steps.
Put 398 + 205 and 367 + 284 on the board; have pairs defend a method for each.
Deal pairs two three-digit number cards; partners solve their sum two ways and compare the number of steps.
Give students grocery prices of $4.95 and $2.05, then $4.87 and $2.46; ask them to choose and explain a method for each total.
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Related Standards
- 6.NOS.B.2.d
Determine and explain when a strategy or algorithm is most efficient.
- 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.
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