To work on your student's 4 digit addition and subtraction skills with regrouping, your student will solve the addition or subtraction problems and then use the key at the top to color the part of that picture the corresponding color. There are 2 pictures for addition and 2 for subtraction. They are the same except one is with black numbers and the others use the Montessori colors for Place Value. These can be used with Pre-K to 6th grade aged children as a center, independent work for homeschoo