The first three figures of a sequence are shown. The table records the number of shaded and unshaded rhombuses in each figure.
- Find the number of unshaded rhombuses in Figure 12?
- Find the number of shaded rhombuses in Figure 69?
- Which figure number has 544 shaded rhombuses?
Figure number |
Number of unshaded rhombuses |
Number of shaded rhombuses |
1 |
1 |
8 |
2 |
4 |
12 |
3 |
9 |
16 |
(a)
Pattern for the number of unshaded rhombuses
Figure 1: 1
2 = 1
Figure 2: 2
2 = 4
Figure 3: 3
2 = 9
Number of unshaded rhombuses = Figure number
2 Number of unshaded rhombuses in Figure 12
= 12
2 = 144
(b)
Pattern for the number of shaded rhombuses
Figure 1: 1 x 4 + 4 = 8
Figure 2: 2 x 4 + 4 = 12
Figure 3: 3 x 4 + 4 = 16
Number of shaded rhombuses = Figure number x 4 + 4
Number of shaded rhombuses in Figure 69
= 69 x 4 + 4
= 276 + 4
= 280
(c)
Number of shaded rhombuses = Figure number x 4 + 4
Figure number = (Number of shaded rhombuses - 4) ÷ 4
Figure number with 544 shaded rhombuses
= (544 - 4) ÷ 4
= 135
Answer(s): (a) 144; (b) 280; (c) 135