This is a GEOMETRIC SEQUENCE...
take note they have a common ratio of 3...
4.5/1.5 = 3
13.5/4.5 = 3
40.5/13.5 = 3
From the FORMULA of Geometric sequence:
a(subscript n) = a₁(r)^n-1
where r = common ratio........3 in this case
n = nth term ..............5 in this case
a5 = (1.5)(3)^5-1
= (1.5)(3)^4
= (1.5)(81)
a5 = 121.5 .................ANSWER
