Question

Natalia is writing a recursive formula to represent the sequence. 8, 12, 18, 27, ... What value should she use as the common ratio in the formula? Write the answer as a decimal rounded to the tenths place.

Answer 1

a = 8, a2 = 12, a3 = 18, a4 = 27,...
12 = r · 8 ⇒ r = 12 : 8 = 1.5
r = 1.5. We can justify it:
18 = 8 · 1.5² = 8 · 2.25 ( true )
27 = 8 · 1.5³ = 8 · 3.375 ( true )