Question

On using anti bacterial drug it has been observed that

(i) The number of bacteria decreases by 4% in the first hour.

(II) The number increases by 5% in the second hour. The number has increased by 10% in the third hour.

(iii) If the number of bacteria is 500,000, then what is the % increase in the number of bacteria at the end of 3 hours.

1. 11.08%
2. 10.88% 
3. 9.58%
4. 10.02%

Answer 1

Correct Answer - Option 2 : 10.88% 

Given:

The number of bacteria decreases in first hour = 4%

The number of bacteria increases in second hour = 5%

The number of bacteria increases in third hour = 10%

Total number of bacteria = 500,000

Time = 3 hours

Calculation:

According to the question

⇒ (500,000 × 96/100 × 105/100 × 110/100)

⇒ (500,000 × 24/25 × 21/20 × 11/10)

⇒ 554,400

Now,

⇒ (554,400 – 500,000)

⇒ 54,400

Required percentage = (54,400/500,000 × 100)

⇒ (272/25)%

⇒ 10.88%

∴ Required percentage increase is 10.88%