2.NBT.7: Add and Subtract Within 1,000
Also written as 2.NBT.B.7 and CCSS.MATH.CONTENT.2.NBT.B.7 · Cluster: Use place value understanding and properties of operations to add and subtract.
The Official Wording
Add and subtract within 1000, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method. Understand that in adding or subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.
Common Core State Standards, Grade 2, Number & Operations in Base Ten · Read it at the source · Checked October 14, 2026
What 2.NBT.7 Means in Plain English
Second graders add and subtract three-digit numbers, like 356 + 278 or 634 − 278, with base-ten blocks or quick drawings: squares for hundreds, lines for tens, dots for ones. Hundreds go with hundreds, tens with tens, and 12 tens trade for a hundred and 2 tens.
The models are the method here, with the written steps tied to them, not a bare algorithm. Fluency within 1,000 is the 3rd grade target (3.NBT.2), and the standard algorithm with multi-digit numbers arrives in 4th grade (4.NBT.4), once regrouping is understood as trading.
2.NBT.7 I Can Statements
- I can add two three-digit numbers with blocks or drawings.
- I can subtract within 1,000, opening a ten or hundred when I need to.
- I can explain my drawing with hundreds, tens and ones.
2.NBT.7 Worked Example
One three-digit sum with two trades in it, drawn and recorded the way the standard asks.
Add 356 + 278. Draw both numbers, then add like with like.
- Draw both numbers: squares for hundreds, lines for tens, dots for ones. Then add like with like, hundreds first.300 + 200 = 500
- Tens with tens: 5 tens and 7 tens are 12 tens. Ten of those lines trade for a new square.50 + 70 = 120
- Ones with ones: 6 dots and 8 dots are 14, a ten and 4 ones. Ten dots trade for a new line.6 + 8 = 14
- Gather the three totals. The 120 gives up a hundred and the 14 gives up a ten.500 + 120 + 14 = 500 + 100 + 20 + 10 + 4
- Six squares, three lines, four dots.356 + 278 = 634
Check it: Estimate first: 356 is near 350 and 278 is near 280, and 350 + 280 = 630, so 634 makes sense. The drawing agrees: 6 squares, 3 lines, 4 dots.
Common Mistakes with 2.NBT.7
Adding digits across places
356 + 278: 3 + 2 = 5, 5 + 7 = 12, 6 + 8 = 14, written 51214
Try this: Draw the numbers as squares, lines and dots so 12 tens is visibly 12 lines, then trade ten lines for one square.
Smaller digit from bigger, no matter where it sits
634 − 278 = 444, from 8 − 4, 7 − 3 and 6 − 2
Try this: Build 634 with blocks and try to take away 8 ones. There are only 4, so a ten has to be opened up first.
Trading without recording it
Knows 14 ones is a ten and 4, writes the 4, then forgets the ten in the tens total
Try this: Record every trade in the drawing: cross out ten dots and draw one new line before adding the tens.
Where 2.NBT.7 Fits
Practice 2.NBT.7
Quick Check
- What is 427 + 385? Which places needed a trade?
- What is 500 − 236?
- The school library has 618 books checked out. 245 come back. How many are still out?