Question

A bacterium divides every 35 minutes. If a culture containing 10${}^5$ cells/mL is grown for 175 minutes, what will be the cell concentration/mL after 175 minutes?

• A. $5\times {10}^5$ cells
• B. $35\times {10}^5$ cells
• C. $32\times {10}^5$ cells
• D. $4.175\times {10}^5$ cells

Answer 1

Answer: (C)

$32\times {10}^5$ cells

A bacteria divides every 35 minutes. Thus the concentration of bacteria gets doubled in every time period of 35 minutes. In 175 minutes, there will be 5 generations of bacteria. Thus, when a culture containing 10${}^5$ cells/ml is grown for 175 minutes the concentration will be 10${}^5$x2${}^5$ = 32x10${}^5$.

So, the correct answer is option C.