SOLUTION: A computer is infected with a virus. Assume that it infects 20 other computers within 5 minutes; and that these PCs and servers each infect 20 more machines within another five mi

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Question 482244: A computer is infected with a virus. Assume that it infects 20 other computers within 5 minutes; and that these PCs and servers each infect 20 more machines within another five minutes, etc. How long until 100 million computers are infected?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
A computer is infected with a virus. Assume that it infects 20 other computers within 5 minutes; and that these PCs and servers each infect 20 more machines within another five minutes, etc. How long until 100 million computers are infected?
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start: 1
5 min: 1*20 = 20
2*5 min: 20*20 = 20^2
3*5 min: 20^3
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x min : 20^(x/5)
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Solve 20^(x/5) = 100 million = 10^8
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(x/5)log(20) = 8
(x/5) = 6.149
x = 30.75 minutes
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Cheers,
Stan H.
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