Give your little one some practice building addition skills with this add 3-digit and 2-digit numbers without regrouping worksheet. In this worksheet, students must find the missing number using the count-on method or the relationship between addition and subtraction. To solve add 3-digit and 2-digit numbers without regrouping worksheet, they do not need to regroup the numbers. In this worksheet, students practice solving problems written in the horizontal format. How numbers are laid out in a problem affects the method a student employs to solve it. Therefore to develop actual fluency and mastery of multiple strategies, students must practice different formats.