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,
- find the total number of squares in Figure 40,
- find the total number of shaded squares in Figure 57.
- what will be the figure number that will have 121 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)
2Number of squares for Figure 40
= (40 x 2 - 1)
2 = 79 x 79
= 6241
(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 57
= ((57 - 1) x 2)
2 = 112 x 112
= 12544
(c)
Number of squares = (Figure number x 2 - 1)
2 Figure number = {(√ Number of squares) + 1} ÷ 2
Figure number with 121 squares
= {(√121 + 1) ÷ 2
= (11 + 1) ÷ 2
= 12 ÷ 2
= 6
Answer(s): (a) 6241; (b) 12544; (c) 6