Question

A bacterium divides once in every 25 minutes. If a culture containing ${10}^4$ cells per ml is grown for 3 hrs short of 5 minutes. What will be the cell concentration per ml?

• A. $64\times {10}^4$
• B. $32\times {10}^4$
• C. $128\times {10}^4$
• D. $256\times {10}^4$

Answer 1

The correct option is C $128\times {10}^4$

Duration = 3 hrs short of 5 mins = so, total hr = 2 hrs 55 mins = 175 mins
Every 25 mins it divides, so for 175 mins it will $\frac{175}{25}=7times$
Formula = Number of cells $=2^n$
It will be $=2^7=128$
As culture contains ${10}^4$ cells initially, thus after 175 mins total cell number will be $128\times {10}^4$