Question

the bacteria in a culture grows by 10 percent in the first hour decreases by 10 percent in the second hour and again increases by 10 percent in the third hour find the bacteria at the end of the third hour if the count was initially 20000

Answer 1

20000×10/100
=22000
22000- 22000×10/100
19800
19800+19800×10/100
21780 is the answer

Answer 2

Answer:

Number of bacteria at the end of 3 hours was 21,780.

Step-by-step explanation:

Given : The bacteria in a culture grows by 10 percent in the first hour decreases by 10 percent in the second hour and again increases by 10 percent in the third hour.

To find : The bacteria at the end of the third hour if the count was initially 20000 ?

Solution :

The number of bacteria initially is 20,000.

In first hour increase in the number of bacteria = 10%

i.e.  10 % of 20,000 = 0.1 × 20,000= 2,000

Number of bacteria till second hour became 20,000+2,000=22,000

In second hour decrease in the number of bacteria = 10%

i.e. 10 % of 22,000 = 0.1 × 22,000 = 2,200

Number of bacteria till third hour is given by,

$N_3$ = number of bacteria till second hour - decrease in the number of bacteria in second

$N_3$ = 22,000 - 2,200 = 19,800

In third hour increase in the number of bacteria = 10%

i.e. 10 % of 19,800 = 0.1 × 19,800 = 1,980

Number of bacteria till fourth hour

$N_4$ = number of bacteria till 3rd hour + increase in the number of bacteria in third hour

$N_4$ = 19,800 + 1,980 = 21,780

Therefore, Number of bacteria at the end of 3 hours was 21,780.