A Casting Out Nines digit sum is a single digit number used for checking your work. A digit sum can be created for any number. Checking your work by Casting Out Nines becomes very easy when you master creating a digit sum.
There are two different techniques that you can use for creating a Casting Out Nines digit sum. Choose the one that is easiest for you.
Technique 1
Eliminate any digits in the number that add up to 9 (including 9 itself).
Example
56593 digit sum is 1
Step 1
Remove any 9's and digits that add up to nine.
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Step 2
Add the remaining digits.
5 + 5 = 10
Step 3
Divide step 2 by 9. The remainder is the Casting Out Nines digit sum (can be zero).
10 / 9 = 1 Remainder 1
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Technique 2
Add each individual digit in the number.
Example
56593 digit sum is 1
Step 1
Add each individual digit in the number.
5 + 6 + 5 + 9 + 3 = 28
Step 2
Keep adding digits in the answers until a single digit is reached.
2 + 8 = 10
1 + 0 = 1
Step 3
The final digit in Step 2 is the Casting Out Nines digit sum. If the final digit is 9 then cast it out leaving the digit sum as 0.
1 is the digit sum for 56593