$ \Rightarrow \omega _1^2 + \omega _2^2$
$ \Rightarrow {\left( {\frac{{2\pi }}{T}} \right)^2} = {\left( {\frac{{2\pi }}{{{T_1}}}} \right)^2} + {\left( {\frac{{2\pi }}{{{T_2}}}} \right)^2}$
$ \Rightarrow T = \sqrt {\frac{{T_1^2T_2^2}}{{T_1^2 + T_2^2}}} $
$ = \sqrt {\frac{{{{\left( {\frac{4}{5}} \right)}^2}{{\left( {\frac{3}{5}} \right)}^2}}}{{{{\left( {\frac{4}{5}} \right)}^2} + {{\left( {\frac{3}{5}} \right)}^2}}}} = 0.48\,sec $
