Maryland Math 2.NOS.C.8.a
The Standard
- 2.NOS.C.8
- Fluently add and subtract within 100.
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.
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 add and subtract by counting on or back, or by working with tens and ones. They show their steps with drawings, number lines, or equations.
What Mastery Looks Like
- A student can solve 38 + 27 by making 40, then adding 25 to get 65. They can solve 64 - 28 by taking away 20, then 8, and explain each step.
Common Misconceptions
- Students may start at 1 instead of counting on from the first number. Some treat the 3 in 38 as three ones, or write 44 for 64 - 28 by subtracting the smaller digit from the larger digit in each column.
How to Assess It
- On an exit ticket, ask: “Solve 38 + 27 and 64 - 28. Show your counting jumps or tens-and-ones steps for each.”
Lesson moves
Ways to Teach It
Give pairs base-ten blocks to build 38 and 27, combine the blocks, trade ten ones for a ten, and write the sum.
Ask, “How could you solve 52 - 19 without counting back 19 times?” Have partners draw jumps and explain their choices.
Make cards for 34 + 28, 51 - 17, 46 + 19, and 72 - 25, plus matching number-line jumps; partners race to match them.
Post a mock library log with 48 books returned Monday and 27 Tuesday; students draw tens and ones to find the total.
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Printable 2.NOS.C.8.a Worksheet
A ready-to-print activity worksheet aligned to 2.NOS.C.8.a, with an answer key for the teacher on its own page. No account needed.
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Related Standards
- 1.NOS.E.10.b
Use counting strategies and strategies based on place value (e.g., partial sums, making tens, etc.) to add.
- 2.NOS.B.6.a
Use counting, make ten, and ten more/less, doubling strategies to add and subtract.
- 1.NOS.E.13.b
Use counting strategies, properties of operations, and/or the inverse relationship between addition and subtraction to subtract.
- 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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