Each figure is made up of a number of identical sticks of 1-cm length.

1. Find the perimeter of Figure 61.
2. Find the number of sticks in Figure 91.
3. Given that a figure has a perimeter, P, of 286 cm, find the number of squares in this figure.

Figure Number	Number of squares	Number of triangles	Perimeter (P)	Number of sticks
1	1	2	6	8
2	2	4	10	15
3	3	6	14	22
4	4	8	18	...
...	...	...	...	...
8	...	...	...	...

(a)
Pattern for perimeter in cm
Figure 1: 1 x 4 + 2 = 6
Figure 2: 2 x 4 + 2 = 10
Figure 3: 3 x 4 + 2 = 14

Perimeter = Figure number x 4 + 2

Perimeter for Figure 61
= 61 x 4 + 2
= 246 cm

(b)
Pattern for the number of sticks
Figure 1: 1 x 7 + 1 = 8
Figure 2: 2 x 7 + 1 = 15
Figure 3: 3 x 7 + 1 = 22

Number of sticks = Figure number x 7 + 1

Number of sticks in Figure 91
= 91 x 7 + 1
= 638

(c)
Perimeter = Figure number x 4 + 2
Figure number = (Perimeter - 2) ÷ 4

Figure number with the perimeter 286 cm
= (286 - 2) ÷ 4
= 284 ÷ 4
= 71

Pattern for the number of squares
Figure 1: 1
Figure 2: 2
Figure 3: 3

Number of squares = Figure number

Number of squares for Figure 71 = 71

Answer(s): (a) 246 cm; (b) 638; (c) 71