The Addition Sort: 11 to 16 Sums can be used as a math center activity or as an anchor activity that students can complete when they are finished their class work. The addition sort is a great way for students to practice their addition skills. Cards and headings are ready to print and use. Students match the addition questions to the headings with the correct sums. Other uses for the addition sort cards are as an addition match game and as a flexible grouping strategy.