The count of bacteria in a sample grows by 24% during the first hour.It decreases by 15% during the next one hour and again decreases by 10% during the third hour. If the present count of bacteria in the sample is 55000, then what will be the net increase/decrease in the count of bacteria after three hours?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. Decrease, 2827.
Let initial count = x
x × 1.24 × 0.85 × 0.90
1.24 × 0.85 = 1.054
1.054 × 0.90 = 0.9486
Net factor ≈ 0.9486 (<1), so net decrease.
Net change = 0.9486 − 1 = − 0.0514, about 5.14% decrease.
Present count = 55000, so initially it was higher by ≈ 5.14%.
Decrease = 55000 × (5.14/100) ≈ 2827
Net decrease of about 2,827 bacteria