|Phyllis Chinn, Ph.D. Professor of Mathematics
Dale Oliver, Ph.D. Professor of Mathematics
Department of Mathematics
Humboldt State University
Arcata CA 95521
The Game of SET®
The SET® deck
called "oval", "diamond" and "squiggle" respectively. Each of these shapes may be colored purple, red or green, and each is either outlined, filled in or striped. For example, the card in figure 1 has number 2, shape oval, color red, and shading striped. No two cards in the deck are identical and each possible choice of one value for each attribute occurs on one card.
When introducing SET® in your classroom, challenge your students to describe the full deck of SET® cards for themselves. Include in this challenge the question "Can you determine without counting the cards one by one, how many cards are in the complete SET® deck?" Let the students have a deck to work with and ask them to figure out the rule by which the deck was constructed, or have the students construct a deck themselves and figure out in advance how many cards they will need. There are many ways children might arrive at the full count, usually involving some sorting of the cards.
The process of counting the SET® deck cards without counting the cards one by one illustrates one the basic counting principles of discrete mathematics, called the multiplication principle. This principle says "if a first event can occur in n ways, and for each of these n ways a second event can occur in m ways, then the two events can occur in m x n ways. Here the "events" are the number of ways to assign attributes to the SET® cards. For any card, one can choose 3 different number of figures to display, combined with one of three shapes for 9 combinations. Each of these 9 combinations can be paired with one of 3 colorings in 9 x 3 = 27 ways, each of which can be paired with 3 shadings for a total of 27 x 3 = 81 cards in the deck.
A 'Set' of Three
To practice your understanding of the definition, see how many 'sets'
you can find in Figure 4.
Did you find the 'set' consisting of:
Notice that the three cards in a 'set' may be different in 1,2,3, or 4 of the attributes. The first person to notice a 'set' in the current layout calls out the word 'set' and then is allowed to touch the three cards. While it is not required in the rules, from a pedagogical point of view it is a good idea for the student to explain how s/he knows it is a 'set' -- for example the first 'set' above would be explained by saying, "they are all purple, all striped, all squiggles, and there is a 1, a 2, and a 3 of them." Assuming the student has correctly identified a 'set' s/he takes the 3 cards. If there are now fewer cards in the layout than at the start (i.e., 12 or 9), the dealer replaces them with three new cards. If all players agree there are no 'sets' in the layout, then 3 more cards are added. Play ends when no new cards are left in the deck and no 'sets' remain in the final array. The official game rules suggest that each player keep his/her own score by counting 1 point for each correctly identified 'set', and a -1 point for each incorrect attempt to identify a 'set'. The winner of the game is the player with the most points after each player has had a turn to deal the entire deck. When using SET® in the classroom, we suggest a modification of the official rules. For beginners, don't exact any penalty for an incorrect attempt to identify a 'set'. Once students understand the game thoroughly, any student who makes an incorrect attempt may be penalized by not being allowed to call 'set'' again until someone else has found a 'set'.
SET® and Discrete Mathematics
Each of the suggested questions may be extended by varying the number of attributes or the number of options for attributes. What about a three-attribute deck with 5 possibilities for each attribute? There would be 125 cards in the deck, with a 'set' defined for a set of 5 cards. The SET® deck is just one of many decks which may be constructed. In this context, the search for patterns is wide open.
There are many other games that can be played with the SET® deck. The game and rules for variations can be obtained from SET Enterprises, Inc. 15402 E. Verbena Dr. Fountain hills AZ 85268. Other variations include the games that can be played with other sets of attribute blocks. For a book with many good ideas of attribute activities see .
For constructing a SET® - type deck of cards as a classroom project, we have two suggestions. First, use common geometrical shapes (for example circle, triangle, and square) instead of oval, diamond, and squiggle. Second, to make the game more accessible to color blind students, use three colors that are less likely to appear identical (for example, black, a middle-toned blue or green or purple, and a light tone of pink or light blue or some similar color). Plastic templates of geometrical shapes are helpful for quick and accurate drawings, and the figures can be filled in or striped while the template is still in place.
As a final suggestion, 'set' is a word with meanings that are easily confused with the particular triples of the game SET®. It might be better for children to call out some other word -- like 'triple' or three or '3-set' or some other word the class selects to describe the particular 'set' for this game.
Despite these minor concerns, the authors think the game of SET® is a wonderful activity to add to the classroom -- it is thought provoking and fun!
 Teacher's Guide for Attribute Games and Problems, Elementary
 Curriculum and Evaluation Standards for School Mathematics, NCTM, 1989.