Some patterns of shaded and unshaded small squares is shown. The unshaded squares are those which lie on the diagonals of the figure. By considering the number patterns,

1. find the total number of squares in Figure 26,
2. find the total number of shaded squares in Figure 49.
3. what will be the figure number that will have 16 squares?

Pattern for number of squares
Figure 1: (1 x 2 - 1)² = 1
Figure 2: (2 x 2 - 1)² = 9
Figure 3: (3 x 2 - 1)² = 25
Figure 4: (4 x 2 - 1)² = 49

Number of squares = (Figure number x 2 - 1)²

Number of squares for Figure 26
= (26 x 2 - 1)²
= 51 x 51
= 2601

(b)
Pattern for the number of shaded squares
Figure 1: ((1 - 1) x 2)² = 0
Figure 2: ((2 - 1) x 2)² = 4
Figure 3: ((3 - 1) x 2)² = 16
Figure 4: ((4 - 1) x 2)² = 36

Number of shaded squares = ((Figure number - 1) x 2)²

Number of shaded squares for Figure 49
= ((49 - 1) x 2)²
= 96 x 96
= 9216

(c)
Number of squares = (Figure number x 2 - 1)²
Figure number = {(√ Number of squares) + 1} ÷ 2

Figure number with 16 squares
= {(√16 + 1) ÷ 2
= (4 + 1) ÷ 2
= 5 ÷ 2
= 2.5

Answer(s): (a) 2601; (b) 9216; (c) 2.5