Question

Let $S_n$ denote the sum of the first $n$ terms of an $A.P$. If $S_4=16$ and $S_6=-48$, then $S_{10}$ is equal to :

• A. - 320
• B. -260
• C. -380
• D. -410

Answer 1

Answer: (A)

2{2a+3d} = 16
3(2a + 5d) = -48
2a + 3d = 8
2a + 5d = -16
d = -12
$\therefore a=22$
$S_{10}$ = 5 {44 - 9 × 12}
= -320