Product with Repdigit can be Split into Parts which Add to Repdigit/Mistake

Source Work

 * The Dictionary
 * $6666$
 * $6666$

Mistake

 * ... if a number is multiplied by a number whose digits are all the same, for example, let $894$ be multiplied by $22,222$, then in this case the right-hand $5$ digits, added to the left-hand portion, form another number with equal digits: $894 \times 22,222 = 19866468$ and $198 + 66,468 = 66666$.

This is only guaranteed to work when the repdigit is strictly longer than the non-repdigit part.

For example:

It sometimes works, but you can't guarantee it: