CCSS.Math.Content.1.NBT.C
The standard
Use place value understanding and properties of operations to add and subtract.
Common Core State Standards for Mathematics
What this standard means
Students need to add and subtract within grade-level numbers by using tens and ones, not just counting every object. They should break numbers apart, make a ten, use known facts, and explain why their method works with drawings, cubes, ten-frames, or equations.
Mastery looks like a child saying, “34 plus 20 is 54 because I added 2 tens,” or “46 minus 9 is 37 because I took 6, then 3 more.” Students often get stuck treating digits separately, mixing up tens and ones, or following a procedure without understanding the regrouping.
Ways to teach it
- Hands-on activity: Give students base-ten blocks and have them build 27 plus 15, trade 10 ones for 1 ten, then record the equation.
- Discussion prompt: Ask, “Would you rather solve 48 minus 20 or 48 minus 19 first, and why?”
- Quick assessment: Show 36 plus 8 and ask students to solve it two ways, using a drawing and an equation.
- Real-world connection: Set up a class store where students buy two items under 50 cents and find the total with dimes and pennies.
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Related standards
- CCSS.Math.Content.1.OA.B
Understand and apply properties of operations and the relationship between addition and subtraction.
- CCSS.Math.Content.4.NBT.B
Use place value understanding and properties of operations to perform multi-digit arithmetic.
- CCSS.Math.Content.2.NBT.B
Use place value understanding and properties of operations to add and subtract.
- CCSS.Math.Content.3.NBT.A
Use place value understanding and properties of operations to perform multi-digit arithmetic.