These are practice cards for addends to 10, 20, 50, and 100. The front of the card has a number 1-20, the back has the same number plus equations revealing the addends to 10, 20, 50, and 100. Print them double-sided, cut them out, laminate them, and put them on a ring. Students can work independently or in partners to memorize their addends to 10, 20, 50, or 100.