Some dots were used to create the figures .
- How many dots were used to create Figure 13?
- A pattern is formed with 221 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 13
= (13 - 1) x 4 + 1
= 49
(b)
Figure number with 221 dots
= (221 - 1) ÷ 4 + 1
= 220 ÷ 4 + 1
= 56
Answer(s): (a) 49; (b) 56