SOLUTION: PLEASE HELP ME !!!!! Contagious disease can spread very quickly. Suppose five people are ill during the first week of an epidemic and that each person who is ill spreads the d

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Question 478250: PLEASE HELP ME !!!!!

Contagious disease can spread very quickly. Suppose five people are ill during the first week of an epidemic and that each person who is ill spreads the disease to four people by the end of the next week. By the end of the tenth week of the epidemic, how many people have been affected by the illness?
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,

5 ill week 1, each spreading to 4 people by the end of the next week...

By the end of the tenth week of the epidemic, how many people have been

 affected by the illness?

{5,20,80,320,...}

Geometric sequence r = 4

a%5Bn%5D+=+5%2A4%5E%28n-1%29

sum%28+a%5Bn%5D%2C+n=1%2C+10+%29 = a(1-r^n)/(1-r)= 5(1-4^10)/(1-4) = 1,747,625