Wyoming Math 2.NBT.7c
The Standard
Add and subtract within 1,000, using concrete models or drawings and strategies based on place value, properties of addition, and/or the relationship between addition and subtraction: Understand that sometimes it is necessary to compose or decompose tens or hundreds.
2023 Wyoming Mathematics Content and Performance Standards · Use 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 three-digit numbers using blocks, drawings, or place-value strategies. They trade between ones, tens, and hundreds when a place reaches ten or runs short.
What Mastery Looks Like
- A student can solve 268 + 157 by making a new ten and then a new hundred. They can solve 402 − 175 by breaking a hundred into tens and a ten into ones, then explain why 227 remains.
Common Misconceptions
- Students may subtract the smaller digit from the larger one in each place and get 373 for 402 − 175. Some trade a hundred for only one ten. Others forget to lower the tens count after breaking a ten into ones.
How to Assess It
- Give students 402 − 175. Ask for a place-value sketch showing each trade and the answer, 227.
Lesson moves
Ways to Teach It
Build 268 + 157 with base-ten blocks, then bundle ten ones into a ten and ten tens into a hundred.
Have partners use a place-value chart to explain why solving 402 − 175 requires breaking a hundred into ten tens.
Give pairs cards with 245 + 138 and 504 − 276, then have them sketch each trade and check each other's answers.
A classroom has 326 pencils and receives 185 more; students sketch the trades needed to find the new total.
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Printable 2.NBT.7c Worksheet
A ready-to-print activity worksheet aligned to 2.NBT.7c, with an answer key for the teacher on its own page. No account needed.
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Related Standards
- 2.NBT.1c
Three-digit numbers can be decomposed in multiple ways (e.g., 524 can be decomposed as 5 hundreds, 2 tens and 4 ones or 4 hundreds, 12 tens, and 4 ones, etc.)
- 1.NBT.4c
Understand that in adding two-digit numbers, adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten.
- K.OA.3
Decompose numbers less than or equal to 10 in more than one way.
- 2.NBT.7b
Understand that in adding or subtracting three-digit numbers, add or subtract hundreds and hundreds, tens and tens, ones and ones.
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