Question 170096:  Ratio and Proportion 
 
2. A new virus is released on the internet; the administrator of a department's Local Area Network ( LAN) is given five minutes by a manager to estimate the impact. The administrator samples 15 of the PCs connected to the LAN, and finds that 9 are infected; use proportion to estimate the number of infected PCs if there are a total of 202 PCs connected to the LAN. 
 
This problem has me totally confused!  Again, I am not good a word problems.  I never know where to start, I have been trying to work out the problem, but I don't know where to begin.  Please help me! 
 Answer by stanbon(75887)      (Show Source): 
You can  put this solution on YOUR website! A new virus is released on the internet; the administrator of a department's Local Area Network ( LAN) is given five minutes by a manager to estimate the impact. The administrator samples 15 of the PCs connected to the LAN, and finds that 9 are infected; use proportion to estimate the number of infected PCs if there are a total of 202 PCs connected to the LAN.  
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Use a proportion: 
[9 infected/15 sampled] = [x infected/all the PCs]
 
(9/15) = (x/202) 
x = 202(9/15)
 
x = 202(3/5) 
x = 121.2 
Round down to get x = 121 infected PC's out of 202 
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Cheers, 
Stan H. 
 
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