If S r denotes the sum of the first r terms of an A.P. Then, S 3n : (S 2n — S n ) is

Question

Philoid · Accepted Answer

S_2n = (2a + (2n–1) d)

S_n = (2a + (n–1)d)

S_3n = (2a + (n–1)d)

S_2n –S_n = (2a + (2n–1) d) – (2a + (n–1)d)

= (2a + (n –1) d)

S_3n: (S_2n — S_n) = (2a + (n–1)d) : (2a + (n –1) d)

= 3