Geometric Gin


by Keely Kelman


Keely Kelman is a graduate student in Educational Technology at San Diego State University. She is a certificated multiple subject teacher.


Instructional Objective The learners will be able to calculate perimeter and area of triangles, squares, rectangles, and trapezoids. They will also be able to categorize triangles by determining whether they are right, isosceles, acute, or obtuse. In the affective domain, the players will enjoy applying their geometric skills in a fun and exciting game.
Learners/Context The learners consist of ninth and tenth grade geometry students. The learners have been studying a geometry unit on shapes, area, and perimeter.

This game is designed as a reinforcer. It could be played concurrently with the unit of study or as a review. It will encourage and allow the learners to apply their geometric knowledge and computation skills.


Rationale This card game is appropriate because it requires the learners to recall specific geometric formulas and criteria just as they would need to for an exam. Although the rules of the game allow for reference to formulas, the learner is often motivated not to use the reference card and therefore puts more effort into recalling the information needed. This game is mobile, easily duplicated, and is designed after a familiar game.

Rules A minimum of two and maximum of four players.

The game is played as follows:

  1. The object of the game is to get 'Gin'. This entails getting a correct combination of three and four cards. As in Gin, the cards must be categorized by 'suit'. The suits for this game are perimeter, area, or triangles. The cards must first be shuffled and seven cards should be dealt to each player. The deck should then be placed face down with one card placed face up as a discard pile. The play goes in a clockwise direction and begins with the player to the left of the dealear. At each players turn, the player has the option to pick the face up card or one from the deck. The player must then discard one card in the discard (face up) pile. Play continues until someone gets 'Gin'. When a player gets 'Gin', he or she must show the cards to the other players and explain what the two groupings of the cards are. The groupings may be of similar triangles, same area, or same perimeter. Beware, different shapes can have the same area or perimeter. The other players should also check the groupings by doing the calculations to ensure the cards were properly grouped. There is also a reference card. This reference card is to be placed face down but not in the deck. It may be used as a 'turn'. If a player is confused or has forgotton a formula, he or she may pick up the reference card and view it for a maximun of 20 seconds. They must then place it face down again. This is considered a 'turn'. Play will then proceed to the next player.


Card Design Each card is labled by its suit in the upper left and lower right hand corners. On each card is a geometric shape and the measurements necessary for any computation. Cards are not drawn to scale.


Deck Design The deck contains three suits: triangles, perimeter, and area. There a total of 48 cards. The triangle suit has four cards each of right, isosceles, acute, and obtuse triangles. The perimeter suit has four triangles, squares, rectangles, and trapezoids. Each triangle, square, rectangle, and trapezoid has different perimeters however, one of each has the same perimeter. (In other words, to match perimeters you will need to find the same perimeter in at least three of the four shapes.) The same goes for the area suit. There are four of each shape. Within each shape, there are different areas but there are equal areas in different shapes.

Sample Cards






Design Process I began by thinking of a common difficulty in math. I immediately came to geometry and started working from there. I wanted to design a game that would be useful, but inviting and fun. I also wanted a game which would be challenging. I decided to use four 2-dimensional shapes: triangles, squares, rectangles, and trapezoids. (However, later in the geometry class, I could see the same game being designed for 3-dimensional shapes such as cones, spheres, cubes, pyramids, etc.) To make it challenging I designed it so that the same areas and perimeters were in different shapes. This requires the player to use multiple formulas and not just the same one. It also allows the learner to see how two different looking shapes can have the same area or perimeter.


Last updated by Keely Kelman on September 28, 1996.

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Educational Technology 670, Fall 1996.