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In an A.P., the first term is $32$ and the last term is $-10$. If the common difference is $-2$, then find the number of terms and their sum.
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Sol. Here $a = 32$, $l = -10$ and $d = -2$
$\therefore 32 + (n - 1)(-2) = -10$ (1/2 Mark)
$\Rightarrow n = 22$ (1/2 Mark)
S$_{22} = \frac{22}{2} \times [32 + (-10)]$ (1/2 Mark)
$= 242$ (1/2 Mark)
$\therefore 32 + (n - 1)(-2) = -10$ (1/2 Mark)
$\Rightarrow n = 22$ (1/2 Mark)
S$_{22} = \frac{22}{2} \times [32 + (-10)]$ (1/2 Mark)
$= 242$ (1/2 Mark)