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In a series -9,-6,-3,----, find the number of terms n to get a sum $S_{n}$ = 66.

$\begin{array}{1 1} -4 \\ 11\\ 8 \\ 6\end{array}$

1 Answer

Answer : (b) 11
Explanation: Observe the series -9,,-6,-3-------
It is an AP with a=-9 ,d=+3
In an AP,sum $S_{n}\;$ is given by
Since number of terms in a series cannot be negative, answer n=11 is valid.
answered Dec 30, 2013 by yamini.v

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