JEE PYQ: Sequence And Series Question 56
Question 56 - 2019 (12 Apr Shift 1)
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:
(1) $-260$
(2) $-410$
(3) $-320$
(4) $-380$
Show Answer
Answer: (3)
Solution
Given, $S_4 = 16$ and $S_6 = -48$
$\Rightarrow 2(2a + 3d) = 16 \Rightarrow 2a + 3d = 8$ …(i)
And $3[2a + 5d] = -48 \Rightarrow 2a + 5d = -16$ [using equation (i)]
$\Rightarrow d = -12$ and $a = 22$
$\therefore S_{10} = \frac{10}{2}(44 + 9(-12)) = -320$
BETA
