A geometric progression has common ratio = 3 and last term = 486. If the sum of its terms is 728; find its first term.

Let n th term be the last term. ⇒ ar n - 1 = 486 ⇒ a(3) n - 1 = 486 ⇒ a.3 n .3 -1 = 486 ⇒ Since, r 1 Hence, first term = 2.