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Homework Help: Sequences and series

  1. Oct 8, 2006 #1
    I am not too sure what to do to answer this question.
    Each year for the past 5 years the population of a certain country has increased by a steady rate of 2.7% per annum. The present population is 15.2 million.
    a) what was thepopulation 1 yr ago?
    b) what was the population 5 years ago?

    I forgot what formula to use. Any help and reminders welcome. Thanks
     
  2. jcsd
  3. Oct 8, 2006 #2

    arildno

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    Well, then re-develop that formula using your head (and our hints).
    You start out!:smile:
     
  4. Oct 8, 2006 #3
    I know the normal formula for compound interest is
    un = u1 * r^(n-1)
    so rearranging that would give u1 = ___(1.027)^5_____
    15.2 * 10^6
     
  5. Oct 8, 2006 #4
    then multiply that answer by (1.027)^(5-1)
     
  6. Oct 8, 2006 #5

    arildno

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    Not sure what you are doing here. "1 year ago from n=1" is n-value n=0.
    Plug that into your equation.
     
  7. Oct 8, 2006 #6
    thanks I have already worked this out, sorry
     
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