Question

A bacterial culture contained 32 × 10⁶ cells after 2.5 hours of exponential growth. If the doubling time was 30 minutes, what was the initial population number in this culture?

• A. 20 × 10⁶ cells
• B. 40 × 10⁵ cells
• C. 16 × 10⁶ cells
• D. 10 × 10⁵ cells

Hint:

Exponential growth is characterized by doubling the population at regular intervals, making it easy to calculate initial populations.

Answer 1

The Correct Option is D

The population doubles every 30 minutes. After 2.5 hours (which is 5 doubling periods), the population increases by a factor of 2⁵ = 32. Thus, the initial population was 32 × 10⁶ / 32 = 10 × 10⁵ cells.