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

How many terms of the series 2 + 6 + 18 + …… must be taken to make the sum equal to 728?

In a G.P., the ratio between the sum of first three terms and that of the first six terms is 125 : 152. Find its common ratio.