If S_n denote the sum of the first n terms of an A.P. If S_2n = 3S_n, then S_3n : S_n is equal to

If S₁ is the sum of an arithmetic progression of 'n' odd number of terms and S₂ the sum of the terms of the series in odd places, then =

If in an A.P., S_n = n²p and S_m = m²p, where S_r denotes the sum of r terms of the A.P., then S_p is equal to

In an AP, S_p = q, S_q = p and S_r denotes the sum of first r terms. Then, S_{p + q} is equal to

If S_r denotes the sum of the first r terms of an A.P. Then, S_3n: (S_2n — S_n) is