What Good Mathematicians Do: poster and bookmark set. These posters are a great addition to any classroom! There are various sizes included to meet the diverse needs of learners and teachers. The full size posters are great for displaying on the board or in a bulletin board. They come with “I can…” and “I know…” statements. The half size posters are great for displaying in a area of limited space. The bookmarks can be printed and glued into math journals or planners.