If the sum of second and tenth terms of an arithmetic sequence is equal to 12, then find the sum of fourth, sixth and eighth terms.

Find the sum of n terms of the arithmetic- geometric sequence.

If the sum of the second , third and fourth terms of a positive term G.P is 3 and the sum of its sixth , seventh and eight terms is 243, then the sum of the first 50 terms of this G.P is :

If the sum of n-term of an arithmetic progression sequence 25,22,19,... is 116 , then find the last term.

If the sum of the first n terms of a sequence is equal to √ (3/ 2) ( n^ 2 − n ) , then the sum of the squares of these terms is equal to

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 sum of the first 23 terms of an arithmetic progression equals that of the first 37 terms , then the sum of the first 60 terms equals .

If the sum of first 11 terms of an arithmetic progression equal that of the first 19 terms, Then, what si the sum of first 30 terms?

If the sum of the first 11 terms of an arithmetical progression equals that of the first 19 terms,then the sum of its first 30 terms,is (A) equal to 0 (B) equal to -1 (C) equal to 1 (D) non unique

The sum of the fourth and twelfth term of an arithmetic progression is 20. What is the sum of the first 15 terms of the arithmetic progression?

The sum of the first n-terms of the arithmetic progression is equal to half the sum of the next n terms of the same progression.Find the ratio of the sum of the first 3n terms of the progressionto the sum of its first n-terms.