In arithmetic sequence the sum of first nine terms 279 and the sum of first twenty terms is 1280 then.
What is the 16th terms of the sequence?

In an arithmetic progression of 50 terms, the sum of first ten terms is 210 and the sum of last fifteen terms is 2565. Find the arithmetic progression.

In an arithmetic progression of 50 terms, the sum of first ten terms is 210 and the sum of last fifteen terms is 2565. Find the arithmetic progression.

If the sum of first p terms of an A.P is equal to the sum of the first q terms , then find the first (p+q) terms .

The sum of first 7 terms of an AP is 63 and the sum of next 7 terms is 161. Find a_(28) .

If the arithmetic progression whose common difference is nonzero the sum of first 3n terms is equal to the sum of next n terms. Then, find the ratio of the sum of the 2n terms to the sum of next 2n terms.

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

Find the sum of first n terms and the sum of first 5 terms of the geometric series 1+ 2/3 +4/9 +............