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

  39
+ 99
 120  (30 + 90) Add the tens
  18  (9 + 9)   Add the units
 138



Vertical Addition by Partition with 3-digit Numbers

  400
+ 835
 1200  (400 + 800) Add the hundreds
   30  (0 + 30)  Add the tens
    5  (0 + 5)    Add the units
 1235


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