This is the fourth strand in a brand new series of Developing Mathematics, developed to be fully in line with the government's Revised Primary Framework for Mathematics. It features completely new content, a fresh up-to-date look both inside and out, and comes with a CD-ROM that contains all of the activity sheets in a customisable format. Using our unique software supplied on the CD-ROM, teachers can effortlessly adapt the activities to make them more challenging or to create further exercises for children who need a bit more practice. New text and images can be easily imported and saved without fear of corrupting the original files, and teachers can print out as many copies as they wish.