Column Addition

Addition grows to three and four digits and is practiced in both column and horizontal form. The work is stacked in stages from no carrying up to four carries, and the same procedure is confirmed again through Fill in the Blank and through word problems on Combining and Increasing.

Where carries come one after another, the small 1 is left out of the next place and the answer falls short by 100 or 1000. Too few digits in the answer points here. In Fill in the Blank, children write down a number that is already visible rather than recovering the missing addend by subtraction.

Handling carries, the work covered in 3-Digit Addition and Subtraction in grade 2, is extended here to addition up to four digits and formalized as column calculation. Writing the digits lined up by place applies without change in the very next unit, Column Subtraction.