Chapter 11 - Further Topics in Algebra - 11.3 Geometric Sequences and Series - 11.3 Exercises - Page 1033: 3

$${a_3} = 24$$

$$\eqalign{ & {\text{Let }}{a_1} = 6,\,\,\,r = 2, \cr & {\text{The }}n{\text{th Term of a Geometric Sequence is}} \cr & {a_n} = {a_1}{r^{n - 1}} \cr & {a_n} = \left( 6 \right){\left( 2 \right)^{n - 1}} \cr & {a_n} = 6{\left( 2 \right)^{n - 1}} \cr & {\text{The term }}{a_3}{\text{ is}} \cr & {a_3} = 6{\left( 2 \right)^{3 - 1}} \cr & {a_3} = 6\left( 4 \right) \cr & {a_3} = 24 \cr} $$