I created this as a review and maintenance activity for early finishers or independent work. Glue page one on one side of the interior of a manila file folder, and cut out the numbers on page two. Laminate, and then add rough velcro to squares for missing numbers and soft velcro on the numbers. Also add one or two rows of rough velcro inside the folder to store the numbers. Mix up the numbers to read 1+4=__ or 1+__=5, and then let the students do the rest!