I noticed that children were discovering the pattern of traditional Montessori booklets and not actually doing the work. Here the isolation of difficulty remains as the first addend remains the same for each page, while the second is mixed (ie: 4 + 1, 4 + 3, 4 + 5... vs 4 + 1, 4 + 2, 4 + 3...). This requires the child to use the materials or at least think about the equation to find the sum. The first addend is red, while the second is black. Each page is outlined in red. Thumbnails to come.