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.

If the sum of 1 + 2 + 2² + …….. + 2^{n - 1} is 255, find the value of n.

The first term of a G.P. is -3 and the square of the second term is equal to its 4^th term. Find its 7^th term.