Question

A cell has a division time of 1 minute. If in 20 minutes it could fill a culture flask by $\frac{1}{8th}$ of its volume, then by what time would the total flask be filled?

• A. 160 mins
• B. 21 mins
• C. 80 mins
• D. 23 mins

Answer 1

The correct option is D 23 mins

Every cell divides once to produce 2 daughter cells in 1 minute. If in 20 mins it could fill $\frac{1}{8th}$ of the volume of a flask, then,

$\Rrightarrow$ In ${21}^{st}$ min =$\frac{1}{8}\times 2=\frac{1}{4},$

$\Rrightarrow$ In ${22}^{nd}$ min =$\frac{1}{4}\times 2=\frac{1}{2},$ and

$\Rrightarrow$ In ${23}^{rd}$ 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.