Question 15 • 2025-2026 FBISD - Precalculus B (CR)
There are 5 bacteria in a petri dish at the start of an experiment. This type of bacteria doubles every 20 minutes. Find the number of bacteria after 4 hours.
Answer
A
40
B
10,240
C
20,480
D
40,960
Explanation
Four hours is 240 minutes, so the bacteria double 240 ÷ 20 = 12 times. The population is 5 × 2¹² = 5 × 4,096 = 20,480 bacteria, which is choice C.
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