Addition by Partitioning




Worked Examples of Addition by Partitioning

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In Years 3/4 children start to lay out numbers to be added vertically, to get ready for the introduction of column addition typically in Years 5/6.
When two-digit numbers are to be added, children are usually taught to add the tens first which gives a rough answer, and then add the units and add those to the total of the tens.
For three-digit numbers, the hundreds are added first, then the tens, and then the units.


Vertical Addition by Partition with 2-digit Numbers

  90
+ 78
 160  (90 + 70) Add the tens
   8  (0 + 8)   Add the units
 168



Vertical Addition by Partition with 3-digit Numbers

  945
+ 323
 1200  (900 + 300) Add the hundreds
   60  (40 + 20)  Add the tens
    8  (5 + 3)    Add the units
 1268


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