Since the sixth term is 1215 and the 5th term is 405, we know each term is 3 times more than the last. Let 'n' represent the first term, then the sum of the first 9 terms can be written as: n+3n+9n+27n+81n+243n+729n+2187n+6561n which sinplifies to 9841n since each term is 3 times the last, the first term must be 405 divided by 3, 4 times in total, which is 5 Now subsitute 'n' for 5, and we get 9841(5) which is 49205 which is the answer.
