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   19 + 99  100  (10 + 90) Add the tens   18  (9 + 9)   Add the units  118 Vertical Addition by Partition with 3-digit Numbers   195 + 205   300  (100 + 200) Add the hundreds    90  (90 + 0)  Add the tens    10  (5 + 5)    Add the units   400

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