Eliminate memory overload and learn 4 math facts on each side of a card! Triangle Flash Cards teach families of facts, showing the relationship between addition and subtraction. How is 4 in one corner related to 7 and 3 in the other corners? For 2 or more players. Each card displays eight problems - four are addition and four are subtraction. Relationship between addition and subtraction facts is emphasized. Students will gain efficiency in memorizing. Cards permit individualization of drill without changing cards. A harder fact is printed on one side of a card and an easier fact is printed on the other side. Includes variations in activities. Supports state and national mathematics standards. Each set includes 20 cards and instructions. Sold as 3 identical sets of flash cards.