A bacteria culture increases by 20% every hour for 3 hours, then decreases by 10% in the 4th hour, and finally increases by 25% in the 5th hour. If the initial count was 5,000, what will be the approximate count after 5 hours?
Show answer & explanation
Correct answer: D
Explanation
Given:
Initial number = 5000
20% increase every hour for the first 3 hours
10% decrease in the fourth hour
25% increase in the fifth hour
First hour = 5000 × 1.20 = 6000
Second hour = 6000 × 1.20 = 7200
Third hour = 7200 × 1.20 = 8640
Fourth hour (10% decrease) = 8640 × 0.90 = 7776
Fifth hour (25% increase) = 7776 × 1.25 = 9720