Gaps

Figure 1 = 3 dots, 3 sticks
Figure 2 = 4 dots, 5 sticks
Figure 3 = 5 dots, 7 sticks..and so forth

Find number of dots in figure 10
Method 1
1) Find the difference of each figures/terms/positions.  In this question, difference = 5-4 = 4-3 = 1 dot
2) To find Figure 10, = Figure 10 x Difference + (1st Figure - difference)
                                 = 10 x 1 + (3-1)
                                 = 12

Find number of sticks in figure 10
1) Find the difference of each figures/terms/positions.  In this question, difference = 7-5 = 5-3 = 2 sticks
2) To find Figure 10, =  Figure 10 x Difference + (1st Figure - difference)
                                 = 10 x 2 + (3-2)
                                 = 21
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When given the total number of dots, find the terms/position/figures.  Example 12 dots belongs to which position/term/figure
Method 1
1) Find the difference of each figures/terms/positions.  In this question, difference = 5-4 = 4-3 = 1 dot
2) To find Figure 10, =  Total dots - (1st Figure number - difference)
                                 = [12- (3-1)] divide by 2
                                 = 5

Method 2
1) Find the difference of each figures/terms/positions.  In this question, difference = 5-4 = 4-3 = 1 dot
2) To find Figure 10, =  [(Term number - 1st Figure number) + 1] divide by difference
                                 = [(12-3) +1] divide by 2
                                 = 5