Chuck Sears There’s a neat trick in accounting related to Rule of 9; it’s often used to detect transposition errors. When two numbers are transposed (for instance, 27 instead of 72), the difference between them is always divisible by 9.
Rule of 9 is widely used in auditing and bookkeeping to quickly spot mistakes.
Origins of the rule are tied to the properties of the base-10 system. The concept has been used in bookkeeping and auditing for decades, helping accountants quickly identify errors in financial records. Although no one is credited with creating this rule, it has been taught extensively in accounting classes and cited in financial publications.
