Each of the figure is made up of 2-cm sticks. The table shows the total length of sticks used for each figure and the perimeter of each figure.
- Complete the table for Figure 9 (i).
- Complete the table for Figure 9 (ii).
- Which figure number will have a perimeter of 180 cm?
(a)
Pattern of the total length of sticks
Figure 1: (1 x 11 + 1) x 2 = 24 cm
Figure 2: (2 x 11 + 1) x 2 = 46 cm
Figure 3: (3 x 11 + 1) x 2 = 68 cm
Formula:
Total length of sticks = (Figure number x 11 + 1) x 2
Total length of sticks for Figure 9
= (9 x 11 + 1) x 2
= 100 x 2
= 200 cm
(b)
Pattern of the perimeter
Figure 1: (1 x 4 + 2) x 2 = 12 cm
Figure 2: (2 x 4 + 2) x 2 = 20 cm
Figure 3: (3 x 4 + 2) x 2 = 28 cm
Formula:
Perimeter of Figure= (Figure number x 4 + 2) x 2
Perimeter of Figure 9
= (9 x 4 + 2) x 2
= 38 x 2
= 76 cm
(c)
(Figure number x 4 + 2) x 2 = 180
Figure number x 4 + 2 = 180 ÷ 2
Figure number x 4 + 2 = 90
Figure number x 4 = 90 - 2
Figure number x 4 = 88
Figure number = 88 ÷ 4
Figure number = 22
Answer(s): (a) 200; (b) 76; (c) 22