The sum of the first 14 terms of an A.P. is 1505 and its first term is 10. Find its 25th term.

Find the geometric progression whose 4th term is 54 and 7th term is 1458.

The fourth term of a G.P. is the square of its second term and the first term is -3. Find its 7th term.

If the 4th, 10th and 16th terms of a G.P. are x, y and z respectively, prove that x, y, z are in G.P.