the bacteria in a culture grows by 10% in the first hour,decreases by 10% in the second hour and again increased by 10% in the third hour. find the bacteria at the end of 3 hours if the count was initially 20000.
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initially , number of bacteria = 20,000
in first hour , increase in the number of bacteria = 10%
= 10 % of 20,000 = 0.1 × 20,000= 2,000
number of bacteria till second hour
= 20,000 + 2,000 = 22,000
now in second hour , decrease in the number of bacteria = 10 % of 22,000
= 0.1 × 22,000 = 2,200
number of bacteria till third hour :
=number of bacteria till second hour - decrease in the number of bacteria in second
= 22,000 - 2,200 = 19,800
in third hour , increase in the number of bacteria
= 10 % of 19,800 = 0.1 × 19,800
= 1,980
number of bacteria till fourth hour
= number of bacteria till 3rd hour + increase in the number of bacteria in third hour
= 19,800 + 1,980 = 21,780
therefore , number of bacteria at the end of 3hours was 21,780 .
Your Answer : 21,780
_______________________________
initially , number of bacteria = 20,000
in first hour , increase in the number of bacteria = 10%
= 10 % of 20,000 = 0.1 × 20,000= 2,000
number of bacteria till second hour
= 20,000 + 2,000 = 22,000
now in second hour , decrease in the number of bacteria = 10 % of 22,000
= 0.1 × 22,000 = 2,200
number of bacteria till third hour :
=number of bacteria till second hour - decrease in the number of bacteria in second
= 22,000 - 2,200 = 19,800
in third hour , increase in the number of bacteria
= 10 % of 19,800 = 0.1 × 19,800
= 1,980
number of bacteria till fourth hour
= number of bacteria till 3rd hour + increase in the number of bacteria in third hour
= 19,800 + 1,980 = 21,780
therefore , number of bacteria at the end of 3hours was 21,780 .
Your Answer : 21,780
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