- This PDF File - 1. Three-Digit Addition Without Regrouping Three-digit addition without regrouping involves adding numbers where the sum in each place value (ones, tens, hundreds) does not exceed 9. Since no column adds up to 10 or more, the digits can be added directly, with no need to carry values over to the next place. This method helps students focus on mastering basic addition skills without the added complexity of regrouping. 2. Three-Digit Subtraction Without Regrouping Three-digit sub