a. Number of rectangles = Figure number
b. Odd Figure number and grey circle/white circles:
Grey/White circles = (nth odd number) x 3.
So, the number of grey/white circles are multiples of 3 for Odd Figure number.
c. Even figure number and grey /white circles:
number of white circle = (number of white circles in preceding Odd figure number) + 1,
number of grey circles = (number of grey circles in preceding Odd figure number + 2)
= (number of white circles in SAME figure number +1)
a) Number of grey circles in Figure 20= 31 + 1 = 32
b) 37 = (37+1)/2 th odd number = 19th odd number
Number of white/grey circles = 19 x 3 = 57
c) 150 is a multiple of 3, so the Figure number is ODD.
150 / 3 = 50
50th odd number = (50×2)-1 = 99
Figure number / number of rectangles = 99