The figures shows a sequence of patterns of an arrangement of dots. "1st row" indicates the number of dots in the first row and the "Total" indicates the number of dots in each pattern.
- Find the number of dots in Figure 8.
- Find the number of dots in Figure 85.
- If the first row of a figure is made up of 100 dots, find the number of dots that make up the figure.
(a)
Pattern for number of dots
Figure 1: 1 x 3 + 4 = 7
Figure 2: 2 x 3 + 4 = 10
Figure 3: 3 x 3 + 4 = 13
Number of dots = Figure number x 3 + 4
Number of dots in Figure 8
= 8 x 3 + 4
= 28
(b)
Number of dots in Figure 85
= 85 x 3 + 4
= 259
(c)
Pattern for number of dots in first row
Figure 1: 1 + 2 = 3
Figure 2: 2 + 2 = 4
Figure 3: 3 + 2 = 5
Figure Number = Number of dots in first row - 2
Number of figure with 100 dots in first row
= 100 - 2
= 98
Number of dots in Figure 98
= 98 x 3 + 4
= 298
Answer(s): (a) 28; (b) 259; (c) 298