Partial sums express whole-number addition as a sequence of place-value-based totals: add hundreds, tens, and ones, or other convenient parts, while maintaining a running total, as in . Each intermediate total represents the quantities accumulated so far, not a separate final answer; the focus is addition within 1,000, supporting accurate written methods without extending to generalized or infinite sums.
To use partial sums, break one number into hundreds, tens, and ones. Add each part to the running total.
Example:
Break into place-value parts:
Now add one part at a time:
So,
The numbers and are partial sums. They show the total so far. The final answer is .
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