Let a be the first term and r the common ratio of the given G.P. Then,
\(a_4\) = 54 and \(a_9\) = 13122
\(\implies\) \(ar^3\) = 54 and \(ar^8\) = 13122
\(\implies\) \(ar^8\over ar^3\) = \(13122\over 54\) \(\implies\) \(r^5\) = 245 \(\implies\) r = 3
Putting r = 3 in \(ar^3\) = 54,
we get a = 2.
Hence, the given G.P is 2, 6, 18, 54, ….
A man saves Rs 200 in each of the first three months of his service. In each of the subsequent months, his saving increases by Rs 40 more than the saving of immediately previous month. His total saving from the start of service will be Rs 11040 after