The 1st term and the common difference of an A.P. are 10,000 and 2000 respectively . Find the sum of the first 12 terms.

The first term and common difference of an A.P. are 3 and 2 respectively. Find the sum of first fifteen terms.

The first term and the common difference of an A.P. are 12 and 4 respectively. If t_n =96 , find n .

If the second term and the fourth terms of an A.P. are 12 and 20 respectively, then find the sum of first 25 terms:

If the second term and the fourth terms of an A.P. are 12 and 20 respectively, then find the sum of first 25 terms:

The first term, common difference and last term of an A.P. are 12,6 and 252 respectively, Find the sum of all terms of this A.P.

The first term and common difference of an A.P. are respectively 4 and 2. If the sum up to n terms is 88, find n.

The first term and common difference of an A.P. are respectively -2 and -4. If the sum upto n terms is —288, find n.

The first term, last term and common difference of an A.P are respectively a, l and 1. Prove that the sum of this A.P. is (1)/(2)(a+b)(1-a+b).

The first term, last term and common difference of an A.P. are respectively a, b and 1. Prove that the sum of this A.P. is (1)/(2)(a+b)(1-a+b) .

The first term, last term and common difference of an A.P are respectively a, l and 1. Prove that the sum of this A.P. is (1)/(2)(a+b)(1-a+b).