Non-tearable, lightweight plastic "flashcards" are more durable than those found in the student materials. Every Fact Triangle consists of three numbers for a "fact family". One number, marked with an asterisk, is the sum or product of the other two numbers. By covering one number with a thumb, children can practice addition/subtraction or multiplication/division facts. Children also recognize the inverse relationship between addition and subtraction and the relationship between multiplication and division. Each set of 36 is packages with a reclosable bag. Overhead sets are also available.