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Number of live viruses

  1. Feb 13, 2012 #1
    1. The problem statement, all variables and given/known data

    A virus give birth to 2 new virus in each second and life span of each virus is 5 seconds.The process of reproduction is continuous until the death of the virus.Initially there is one newly born virus at time t=0.Find the total number of live viruses just after 10 seconds.

    2. Relevant equations

    number of viruses born - number of viruses dead

    3. The attempt at a solution

    Number of born viruses = 1+2+4+8+...+1024
    Number of viruses dead = 0x4+(1+2+4+...+64)

    there fore, answer = 27+28+29+210

    but the given answer is 35(35-1)
    Nowhere near!!!!

    pls help......
  2. jcsd
  3. Feb 13, 2012 #2


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    3^5*(3^5-1)=58806. Even if no viruses die, that's way to big be the answer after 10 seconds. If that's the given answer, there is something wrong with it. But your answer isn't right either. Dead viruses don't reproduce.
  4. Feb 13, 2012 #3
    Sir, i can't get you ... can you explain a bit more???
    you mean that no more viruses reproduce after 5 seconds?
  5. Feb 14, 2012 #4


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    I mean that the ones that have died don't contribute to the count of born ones. Try working this out as a table. At t=4 you have 16. At t=5 you have 32, then you remove the old one so you get 31. How many at t=6?
  6. Feb 14, 2012 #5
    Ohhhh......i missed that point.....

    thanks sir.....you was very helpful.....
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