RRB Paramedical Staff Nurse Model Paper 6

Every cell divides once to produce 2 daughter cells in 1 minute. If in 20 mins it could fill $\frac{1}{8\mathit{t}\mathit{h}}$ of the volume of a flask, then.
$\Rightarrow \ln {21}^{\mathit{s}\mathit{t}}\min =\frac{1}{8}\times 2=\frac{1}{4}$
$\Rightarrow \ln {22}^{\mathit{n}\mathit{d}}\min =\frac{1}{4}\times 2=\frac{1}{2},$ and
$\Rightarrow \ln {23}^{\mathit{r}\mathit{d}}\min =\frac{1}{2}\times 2=1,$ or the entire. So the time taken by the cells to fill the entire flask would be 23 mins.