A G.P. has first term 729 and 7th term 64. Find the sum of its first 7 terms.

The first term of a GP is 27 and its 8th terms is 1/81 . Find the sum of its first 10 terms.

The sum of first 5 terms and first 15 terms of an A.P. are equal. Find the sum of its first 20 terms.

The sum of first 8 terms of an A.P. is 64 and that of first 15 terms is 225. Find the sum of its first 17 terms.

The 12th term of an AP is -13 and the sum of its first four terms is 24. Find the sum of its first 10 terms.

If the sum of first 7 terms of an A.P. is 49 and that of 17 terms is 289, find the sum of first n terms.

The sum of first three terms of a G.P. is 15 and sum of next three terms is 120. Find the sum of first n terms.

The sum of first 8 terms and first 24 terms of an A.P. are equal. Find the sum of its 32 terms.

The sum of the first 7 terms of an AP is 63 and the sum of its next 7 terms is 161. Find the 28 th term of this AP.