Each of the figure is made up of 5-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 1590 cm?
(a)
Pattern of the total length of sticks
Figure 1: (1 x 11 + 1) x 5 = 60 cm
Figure 2: (2 x 11 + 1) x 5 = 115 cm
Figure 3: (3 x 11 + 1) x 5 = 170 cm
Formula:
Total length of sticks = (Figure number x 11 + 1) x 5
Total length of sticks for Figure 9
= (9 x 11 + 1) x 5
= 100 x 5
= 500 cm
(b)
Pattern of the perimeter
Figure 1: (1 x 4 + 2) x 5 = 30 cm
Figure 2: (2 x 4 + 2) x 5 = 50 cm
Figure 3: (3 x 4 + 2) x 5 = 70 cm
Formula:
Perimeter of Figure= (Figure number x 4 + 2) x 5
Perimeter of Figure 9
= (9 x 4 + 2) x 5
= 38 x 5
= 190 cm
(c)
(Figure number x 4 + 2) x 5 = 1590
Figure number x 4 + 2 = 1590 ÷ 5
Figure number x 4 + 2 = 318
Figure number x 4 = 318 - 2
Figure number x 4 = 316
Figure number = 316 ÷ 4
Figure number = 79
Answer(s): (a) 500; (b) 190; (c) 79