Question

If S_r denotes the sum of r terms of an AP and $\frac{S_{a}}{a^{2}} = \frac{S_{b}}{b^{2}} = c$ then S_c is

• A. c³
• B. c/ab
• C. abc
• D. a + b + c

Answer 1

Answer: (A)

c³

Answer 2

S_a = a²c ̃ $\frac{a}{2}$ [2x + (a – 1) d] = a²c

̃ 2x + (a – 1) d = 2ac

Similarly 2x + (b – 1) d = 2bc

d = 2c and x = c

S_c = $\frac{c}{2}$ [2x + (c – 1)d] = c³