Addition 113
Here is an example:
1 2 3 4 5
6 7 8 9 0
4 1 7 3 5
- 2 1 8 6 5
We add the numbers to get our total of 143,835.
Is our answer correct? Let’s check by casting out nines, or working
with our substitute numbers.
1 2 3 4 5 6
6 7 8 9 0 21 3
4 1 7 3 5 11 2 - 2 1 8 6 5 13 4
1 4 3 8 3 5 6
Our substitutes are 6, 3, 2 and 4. Th e fi rst 6 and 3 cancel to leave us
with just 2 and 4 to add.
2 + 4 = 6
Six is our check or substitute answer.
Th e real answer should add to 6. Let’s see.
After casting nines, we have:
1 + 4 + 3 + 8 + 3 + 5 = 6
Our answer is correct.
But there is a further shortcut when you are casting nines to check
a calculation in addition. You can cast out (cross out) any digits
anywhere in the addition that add to 9. You can’t, of course, cross
out digits in the answer with digits you are adding. So, you could
have cast out the 6 in the fourth number with the 3 in the third,
the 7 in the third number with the 2 in the fourth. You could have
cast out every digit in the top two numbers, as each digit in the top