Some dots were used to create the figures .
- How many dots were used to create Figure 18?
- A pattern is formed with 505 dots. Which figure would it be?
(a)
Pattern for the number of dots
Figure 1: (1 - 1) x 4 + 1 = 1
Figure 2: (2 - 1) x 4 + 1 = 5
Figure 3: (3 - 1) x 4 + 1 = 9
Formula
Number of dots = (Figure number - 1) x 4 + 1
Number of dots for Figure 18
= (18 - 1) x 4 + 1
= 69
(b)
Figure number with 505 dots
= (505 - 1) ÷ 4 + 1
= 504 ÷ 4 + 1
= 127
Answer(s): (a) 69; (b) 127