The first and the last terms of an A.P. are 34 and 700 respectively. If the common difference is 18, how many terms are there and what is their sum?

In an A.P. the first term is 25, n^th term is -17 and the sum of n terms is 132. Find n and the common difference.

Find the A.P. whose 4^th term is 9 and the sum of its 6^th term and 13^th term is 40.

The sum of n natural numbers is 5n² + 4n. Find its 8^th term.