4 ms·
How is this different from "casting out tens," or just checking the accuracy of the digit in the ones place?
by cproctor 11y ago
How is this different from "casting out tens," or just checking the accuracy of the digit in the ones place?
- dkbrk 11y agoThis method uses all the digits in the number so that it is possible to detect an error in any position, not just in the least-significant digit.
- contravariant 11y agoThe idea is that you can also just add up the digits of a number to 'cast out nines' (during this calculation you can also ignore any pair of digits that adds up to 9). By the way, you can combine this with 'casting out tens', then you'll know if your result is accurate mod 90 (which is even less likely than it being accurate mod 10 or mod 9, if you've made a mistake).