2. The Partial-Sums Algorithm Used for adding multi-digit numbers. Used for adding multi-digit numbers. Created by Paula Cantera Elk Neck Elementary

3. Children should be encouraged to check their answers to see whether they make sense.  Whether done in advance or as a final check, it is desirable to make a “ballpark estimate” of the answer.

4. One way to make a “ballpark estimate” is to round each addend to the nearest ten or hundred, depending on the numbers being added.

5. For example: 63 + 24 is close to 60 + 20. Students can easily add 60 + 20 to get 80. Any answer not close to 80 would not be a reasonable answer and should be checked for accuracy.

6. When using the partial-sums algorithm, the partial sums may be calculated in any order - it does not matter whether you add the tens first or the ones first.

7. Think of each addend in its expanded form: 63 24 60 + 3 20 + 4 +

8. Now add the tens 80 63 24 60+3 20+4 60+ 20

9. Next add the ones 80 63 24 60+3 20+4 60+ 20 3+ 4 7 + +

10. Finally, add the partial sums. 80 63 24 60+3 20+4 60+ 20 3+ 4 7 + + 87

11. Of course this can be expanded to work with 3-digit numbers, and 4-digit…….

12. 342 145+ 300 + 40 + 2 100 + 40 + 5 400 80 7 + 487

13. Partial-Sums Algorithm Just one way to add multi-digit numbers. Try some at home today! Just one way to add multi-digit numbers. Try some at home today!