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-   -   Logarithmic functions (https://www.askmehelpdesk.com/showthread.php?t=95382)

  • May 23, 2007, 11:38 PM
    sim0nz12345
    Logarithmic functions
    Could you please help me with this difficult question.

    It is estimated that the population, N, of two towns, Princetown (P) and Queensbridge (Q) will increase according to the law:

    N=A10^(kt) where t is the number of years reckoned from 1994

    If their populations were:

    P: 20 000 in 1994 and 26 400 in 1997
    Q: 10 000 in 1994 and 11 560 in 1997

    a) Calculate the values of the constant A and k
    b) What will be the population of P in the year 2010?
    c) During what year will the population of Q double?
  • May 23, 2007, 11:51 PM
    Capuchin
    for a) you can use the case where t = 0 to get a value for A, then you can use the case where t > 0 to find out the value of k.

    for b) once you know A and k it's trivial to put in the right t.

    for c) you need to find t where you should be able to easily derive an expression that gives you t.
  • May 24, 2007, 12:17 AM
    sim0nz12345
    Thank you very much appreciated

    But I didn't quite understand part a)
    I'm sorry
  • May 24, 2007, 12:20 AM
    Capuchin
    Okay so for Q we have N=A10^(kt), t = 0, N = 10000

    so you can solve 10000 = A10^(0k) = A10^0

    There's only 1 variable, A, so you can work out it's value.

    Now you put your value for A into the equation with the 2nd t value for which you have a value of N. Then you will have k as the only variable. And you can solve to find it.
  • May 24, 2007, 12:27 AM
    sim0nz12345
    Ok cool
    WOW you respond quickly
    Thanks
  • May 24, 2007, 12:59 AM
    sim0nz12345
    Sorry again but what is the variable of A and then of k
    I did the working out but came up weird and wrong answers.
    I know this must be frustrating but yeah...
    Thanks again last time
  • May 24, 2007, 04:10 AM
    Capuchin
    For P:



















  • May 24, 2007, 04:55 AM
    sim0nz12345
    I've got everything you explained so far...
    With b) being 87948.8 I think

    But I don't know c) even after you explained it to me

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