This is a problem set used in the second semester of third grade at Waseda Academy. I purchased the materials after enrolling before starting fourth grade, but by the time they arrived, the classes were already using fourth-grade materials, so I never used them. All materials include explanations and answers. They have been stored at home, so there may be some minor scratches. Please refrain from purchasing if you are sensitive to such imperfections. I am not offering individual sales of the items.