Casting Out Elevens is a slightly slower but more accurate way to sanity check your work. It is a great way to catch most errors including digit reversals (transposing two digits).
Casting Out Elevens can be used when subtracting numbers of any size.
Example
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Step 1
Find the digit sum for each number being subtracted.
93843 digit sum is 2
13820 digit sum is 4
Step 2
Subtract the two digit sums.
2 - 4 = -2
If the result in step 2 is less
than 0 then add 11 to the result
-2 + 11 = 9
Step 3
Find the digit sum for the subtraction problems answer.
80023 digit sum is 9
Step 4
The subtraction problems answer is probably correct if the digit sums found in Step 2 and Step 3 are the same.
9 = 9 so 80023 is probably correct