Chemistry - Chemical Kinetics Question with Solution | TestHub

Two substances$\mathrm{A}\left({\mathrm{t}}_{\frac{1}{2}}=5\hspace{0.17em}\mathrm{m}\mathrm{i}\mathrm{n}\right)$and$\mathrm{B}\left({\mathrm{t}}_{\frac{1}{2}}=15\hspace{0.17em}\mathrm{m}\mathrm{i}\mathrm{n}\right)$follow first order kinetics, are taken in such a way that initially$\left[\mathrm{A}\right]=4\left[\mathrm{B}\right]$. The time after which the concentration of both substances will be equal is: