Question 983637:  An influenza virus is spreading among a village population.  Every day the number of people who are infected is doubled. If it takes (16)  days to have all the people in that village infected by this virus, how long it will take to have half of them infected? 
 Answer by Boreal(15235)      (Show Source): 
You can  put this solution on YOUR website! it is 2^16/2
 
Take ln of this 
16 ln 2-ln 2 
15 ln 2 
That is 10.3972 
Now raise it to the e power to remove the ln. 
32768.
 
Way 2. 
2^10=1024 
2^11=2048, and 4096,8192,16384,32,768,65536.
 
2^16 is 65536, 2^15 is half that.
 
Way 3: 
It doubles each day. 
Therefore on Day 16, it has doubled from day 15. 
Therefore day 15 is when half are infected. 
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