[tex]\\ \rm\Rrightarrow T=2\pi\sqrt{\dfrac{l}{g}}[/tex]
[tex]\\ \rm\Rrightarrow T^2=4\pi ^2\dfrac{l}{g}[/tex]
[tex]\\ \rm\Rrightarrow l=\dfrac{T^2g}{4\pi^2}[/tex]
If we solve it we get it in between 60 -80
So
Our average breath rate is 17-20
So the ratio will come near 4+
