Question 68495: An ecoli bacteria divides every 20 minutes. After 120 minutes how many ecoli bacteria are there? Solve algebraically.
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! An ecoli bacteria divides every 20 minutes. After 120 minutes how many ecoli bacteria are there? Solve algebraically.
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A(t) = Ao (2)^(t/20)
Assuming you start with 1 bacteria you get:
A(120)=1(2)^(120/20)
=2^6=64
That is the number generated in the last 20 minutes.
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The total number = 1+2+4+....+64
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This is a geometric series with seven terms, a(1)=1, r=2:
S(7)= [r^(8)-1}/[r-1]= 127
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Cheers,
Stan H.
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