Question

1,3,9,27 what's the common ratio

Answer 1

common ratio means
"something" is multiplying the current term, to get the next one

so
if you divide the "next" term by the "current" one
that will spit out that "something"

Answer 2

In general it is, \(\large\color{midnightblue}{ \rm r= a_{n+1}\div a_n }\), and in this case,

\(\large\color{midnightblue}{ \rm r= 27\div9 }\) or \(\large\color{midnightblue}{ \rm 9\div 3 }\) or \(\large\color{midnightblue}{ \rm 3 \div 1 }\)