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3rd Grade Math
12. 3.NBT.A.3
12.6 Simplifying Addition by Separating
Simplifying Addition by Separating: Partial Sums Method
Break bigger numbers into hundreds, tens, and ones, add each part separately, then combine the partial sums for a fast, reliable total.
What You'll Learn
Break each addend apart into hundreds, tens, and ones before adding, such as splitting 234 into 200, 30, and 4.
Add the matching place value parts together to find each partial sum.
Combine all the partial sums into one final total, since \( 300 + 80 + 12 = 392 \).
Recognize that separating numbers turns one hard problem into several easy ones.
Check the final answer by comparing it to an estimate found by rounding the addends.
Apply the same separating strategy to three digit numbers, and later to larger numbers, using place value.
What You'll Practice
1
Splitting two and three-digit numbers into place values
2
Adding numbers up to 999 using separation strategy
3
Filling in missing place values in separated addition problems
Why This Matters
Breaking numbers into place values is a mental math strategy that helps you add quickly and accurately without a calculator. This foundational skill builds number sense and prepares you for multi-digit operations throughout your math education.
This Unit Includes
1 Video lesson
Practice exercises
Learning resources
Skills
Place Value
Addition
Mental Math
Number Decomposition
Number Sense
OH Curriculum Aligned