An open organ pipe and closed pipe have same length.  The ratio of frequencies of their nth overtone is    

In open pipe nth over tone = (n+1) harmonic
${\mathrm{f}}_1=(\mathrm{n}+1)\frac{\mathrm{V}}{2\mathrm{l}}$ 
In closed pipe nth over tone = (2n+1) harmonic
$\begin{array}{l}{\mathrm{f}}_2=(2\mathrm{n}+1)\frac{\mathrm{V}}{4\mathrm{l}}\\ \frac{{\mathrm{f}}_1}{{\mathrm{f}}_2}=\frac{2(\mathrm{n}+1)}{2\mathrm{n}+1}\end{array}$