$$ \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 $n=$
  1. 11
  2. 10
  3. 9
  4. 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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