Octal Number Addition

Addition of Octal Numbers

The addition of octal numbers is not difficult provided you remember that anytime the sum of two digits exceeds 7, a carry is produced.

Compare the two examples shown below:

The octal addition table below will be of benefit to you until you are accustomed to adding octal numbers. To use the table, simply follow the directions used in this example:

Add: 6 base 8 and 5 base 8

Locate the 6 in the X column of the figure. Next locate the 5 in the Y column. The point in area Z where these two columns intersect is the sum. Therefore,

If you use the concepts of addition you have already learned, you are ready to add octal numbers.

Work through the solutions to the following problems:


As was mentioned earlier in this section, each time the sum of a column of numbers exceeds 7, a carry is produced. More than one carry may be produced if there are three or more numbers to be added, as in this example:

The sum of the augend and the first addend is 6 base 8 with a carry. The sum of 6 base 8 and the second addend is 5 base 8 with a carry. You should write down the 5 base 8 and add the two carries and bring them down to the sum, as shown below:


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