Wyoming Math 2.NBT.7b
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 in adding or subtracting three-digit numbers, add or subtract hundreds and hundreds, tens and tens, ones and ones.
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 by working with hundreds, tens, and ones. They use blocks or drawings to show trades when they need more ones or tens.
What Mastery Looks Like
- A student can solve 264 + 158 by combining matching places and trading 10 ones for a ten, then 10 tens for a hundred. They can solve 523 − 178 by drawing the trades and explaining why each one is needed.
Common Misconceptions
- Some students subtract the smaller digit from the larger digit in each place, even when the larger digit is on the bottom. Others trade a ten for 10 ones but forget to remove that ten. In addition, students may leave 12 ones in the answer instead of trading them for a ten.
How to Assess It
- Exit ticket: Solve 523 − 178 with a base-ten drawing. Circle each trade and write why you made it.
Lesson moves
Ways to Teach It
Give pairs base-ten blocks to build 264 and 158, combine matching places, and trade 10 ones or 10 tens when needed.
Ask: Why do you need to trade a hundred for 10 tens when subtracting 178 from 523? Show it in a drawing.
Deal digit cards to build two three-digit numbers, subtract the smaller from the larger, and check each trade with a sketch.
Show a library sign with 523 books and 178 checked out; have students sketch place-value trades to find how many remain.
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Printable 2.NBT.7b Worksheet
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