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 4 (i).
- Complete the table for Figure 4 (ii).
- Which figure number will have a perimeter of 172 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 4
= (4 x 11 + 1) x 2
= 45 x 2
= 90 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 4
= (4 x 4 + 2) x 2
= 18 x 2
= 36 cm
(c)
(Figure number x 4 + 2) x 2 = 172
Figure number x 4 + 2 = 172 ÷ 2
Figure number x 4 + 2 = 86
Figure number x 4 = 86 - 2
Figure number x 4 = 84
Figure number = 84 ÷ 4
Figure number = 21
Answer(s): (a) 90; (b) 36; (c) 21