A culture of yeast contains 20 cells and the number of cells doubles every 30 minutes. How many cells will be present after 2 hours?
Answer
320 cells
The correct answer is 320 cells — Therefore, 320 cells will be present after 2 hours.
Step-by-step solution
- Convert 2 hours into minutes: 2 hours = 120 minutes.
- Determine the number of doubling intervals: 120 minutes ÷ 30 minutes per doubling = 4 doublings.
- Use the formula N = N₀ × 2ⁿ, where N₀ = 20 and n = 4.
- Calculate 2⁴ = 16; then N = 20 × 16 = 320.
- Therefore, 320 cells will be present after 2 hours.
Common mistake: Counting only 3 doublings instead of 4, leading to 160 cells.
Concept tested: Asexual reproduction – growth rate
Published · How this solution was prepared and checked
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