In this lesson, learners are given six sets of cards, each in a different colour. To start the sets of cards are presented in a strip (not cut up) as shown in Figure 1, and each strip of cards describes a particular quadrilateral (square, rectangle, parallelogram, rhombus, trapezium and kite) by providing some of the properties of this quadrilateral. Some of the cards also provide information about the measurements of the quadrilateral.

The idea is that the learners first determine which quadrilateral each strip describes, and they then sketch and name the quadrilateral, marking the features such as parallel and/or equal lines, equal angles and so on. After this they cut the strips into little cards and select the smallest set that is needed to determine the quadrilateral (including its size) (see Figure 2).

In some cases more than one set of cards can be chosen. For example, the strip of cards labelled A1 to A5, shown below (Figure 3) describe a square. Cards A4 and A5 are enough to tell that it is a square, and A2 is needed to know how big the square is. On the other hand, cards A1 and A3 can be used to determine that it is a square and A2 is needed for the size.

 A1The diagonals of the shape are equal A2The shape has at least one side that is 5cm long A3The diagonals of the shape bisect each other at right angles A4The shape has 4 equal angles A5The shape has two pairs of parallel sides

Figure 3: Cards A1 to A5

To finish off, teachers hand out big versions of the little cards and use these to support a whole class discussion. For example, student groups can be asked to come to the board and stick up the cards they chose for a quadrilateral, explaining their reasoning.

The lesson is a minor adaptation of one developed by the University of Nottingham.