Question

A bacterium divides every 20 minutes. If a cultures containing ${10}^6$ cells per ml is grown for 120 minutes, what will be the cell concentration per ml after 120 minutes ?

• A. $32\times {10}^6$ cells
• B. $64\times {10}^6$ cells
• C. $16\times {10}^6$ cells
• D. $120\times {10}^6$ cells

Answer 1

The correct option is A $32\times {10}^6$ cells

A bacterium divides into two daughter cells by fission. Therefore in first 20 minutes, 10$\left(6\right)$ cells will form 2 x 10$\left(6\right)$ bacterium cells. In next 100 minutes, it will undergo 5 more divisions, so by exponential growth law, it will form 2$\left(5\right)$ x 10$\left(6\right)$ cells I.e., 32 x 10$\left(6\right)$ cells in total.

So, the correct answer is option A.