$$ \text { If }\left(1+\frac{3}{1}\right)\left(1+\frac{5}{4}\right)\left(1+\frac{7}{9}\right)…
$$
\text { If }\left(1+\frac{3}{1}\right)\left(1+\frac{5}{4}\right)\left(1+\frac{7}{9}\right) \ldots\left(1+\frac{2 n+1}{n^2}\right)=121 \text {, }
$$
then $n=$
- 11
- 10
- 9
- 8
Solution
We have,
$
\begin{array}{ll}
\left(1+\frac{3}{1}\right)\left(1+\frac{5}{4}\right)\left(1+\frac{7}{9}\right) \ldots\left(1+\frac{2 n+1}{n^2}\right)=121 \\
\Rightarrow \quad \text { (4) }\left(\frac{9}{4}\right)\left(\frac{16}{9}\right) \ldots\left(\frac{n^2+2 n+1}{n^2}\right)=121 \\
\Rightarrow n^2+2 n+1=121 \Rightarrow(n+1)^2=121 \\
\Rightarrow n+1=11 \Rightarrow \quad n=10
\end{array}
$
Asked in: AP EAMCET 2018 (23 Apr Shift 1)
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