Each of the figures is made up of 1-cm wooden rods.
The table shows the number of wooden rods used to make the figures and their perimeters.

1. Find the number of wooden rods in Figure 20.
2. What is the perimeter of Figure 148?
3. Which figure requires a total number of 3911 wooden rods?

(a)
Pattern for the number of wooden rods
Figure 1: 1 x 8 + 7 = 15
Figure 2: 2 x 8 + 7 = 23
Figure 3: 3 x 8 + 7 = 31

Formula:
Number of wooden rods = Pattern number x 8 + 7

Number of wooden rods in Figure 20
= 20 x 8 + 7
= 167

(b)
Pattern for the perimeter of the figure
Figure 1 = 1 x 2 + 7 = 9
Figure 2 = 2 x 2 + 7 = 11
Figure 3 = 3 x 2 + 7 = 13

Formula:
Perimeter of the figure = Pattern number x 2 + 7

Perimeter of figure 148
= 148 x 2 + 7
= 303

(c)
Figure number x 8 + 7 = 3911
Figure number x 8 = 3911 - 7 = 3904
Figure number = 3904 ÷ 8 = 488

Answer(s): (a) 167; (b) 303; (c) 488