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Learning by Doing

objective: To multiply two linear algebraic expressions (polynomials)
using strips of cardboard.

Materials Required: Cardboard, Coloured papers (green, blue, and red),
Geometry box, Cutter, Eraser, Adhesive, Sketch pen.

Preparation:
• Take three pieces of cardboard and cover them with green,
blue, and red coloured papers. x x
1
• From the green cardboard, cut out a large number of x 1 1
squares, each of side length x units (see Fig. 1). Fig. 1 Fig. 2 Fig. 3

• From the blue cardboard, create several rectangles that measure x units by 1 unit, and cut
out several squares measuring 1 unit by 1 unit from the red paper (refer to Fig. 2 and 3).
Procedure:
• Represent the algebraic expression (4x + 6), using the blue and red strips as shown in Fig. 4.

Fig. 4
• Again, represent the expression (3x + 4) using the blue and red strips as shown in
Fig. 5.
• Create a rectangle whose length is (4x + 6) and width is (3x + 4) as shown in Fig. 6.
(4x + 6)
x x x x 1 1 1 1 1 1

x

x

(3x + 4) x Fig. 5

1

1

1

1

Fig. 6

213 Algebraic Expressions