Sum of First n terms of an A.P

Let S_(n) be the sum of first n terms of and A.P. If S_(3n)=5S_(n) , then find the value of (S_(5n))/(S_(n)) is.

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

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

If sum of first 20 terms of an A.P. is equal to sum of first 30 terms of the A.P. then sum of the first 50 terms of the A.P. is

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

If the sum of first 10 terms of an A.P is 60 and sum of first 15 terms is -165 then find the sum of its n terms

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