The first term of an A.P. is 5, the last term is 45 and the sum is 400. Find the number of terms and the common difference.

Find the sum of the first 25 terms of an A.P. whose second and third terms are 14 and 18 respectively.

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

In an A.P., the sum of first n terms is . Find its 25^th term.

Let there be an A.P. with first term ‘a’, common difference, d. Ifdenotes its n^th term andthe sum of first n terms, find.

(i)

(ii)

(iii)

(iv)

(v)

(vi)