Same Math › Grades 2–3 › Partial sums
What is the partial sums method?
Partial sums adds each place separately, hundreds with hundreds, tens with tens, ones with ones, then adds those results together. There's no carrying, because nothing gets squeezed into one column.
- Add each place on its own line: hundreds, tens, ones.
- Write the full value, like 120, not just 12 in the tens column.
- Add the lines: 500 + 120 + 12 = 632
Why schools teach it
Kids always know what each number means
Second graders add within 1,000 using strategies based on place value (2.NBT.B.7). Partial sums is one of the clearest: split each number with expanded form, add like places, then combine.
Carrying hides what's happening ("carry the 1" is really "carry a ten"). Partial sums keeps every value visible, so the stacked method makes more sense when it arrives.
At the kitchen table
What to say, and what to skip
Say this
What do the hundreds add up to?
Is that 4 + 8 or 40 + 80?
Keeping the zeros is the whole point.Can you start with the ones instead?
Any order works. Many kids like starting with the biggest place.Does your answer seem about right?
300 + 300 is 600, so 632 makes sense.
Skip this
Just carry the one.
The stacked method comes later. Partial sums shows why carrying works.- Writing 12 in the tens line.40 + 80 is 120. Writing 12 loses the place value.
Too many lines.
The lines are what make it clear. Speed comes later.
See it in action
Adding 58 + 36 with partial sums
Add the tens
50 + 30 = 80Add the ones
8 + 6 = 14Combine the partial sums
80 + 14 = 94
The 14 is where carrying would happen. Here it's just added at the end.
Free practice sheet
Make a partial sums sheet
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Parents also ask
Does the order of the lines matter?
No. Many classes start with the biggest place, which is the opposite of the stacked method.
How is this different from the method we learned?
Same math. The stacked method combines the lines by carrying; partial sums writes them out.
Does it work with subtraction?
Not as easily, because some places can go negative. Classes use counting up or other strategies for subtraction.
When will my child use the standard method?
Fluency with the standard algorithm for adding and subtracting is a 4th-grade standard (4.NBT.B.4).