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Math Help - Homework help fast...please

  1. #1
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    Homework help fast...please

    a populaton increases from 81,500 to 103,200 over a 7 year period. If the growth rate remians the same how long will it take the initial population to double?
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Jenny Service View Post
    a populaton increases from 81,500 to 103,200 over a 7 year period. If the growth rate remians the same how long will it take the initial population to double?
    assuming exponential growth, we have

    P(t) = P_0 e^{rt}

    where P(t) is the population after time t, P_0 is the initial population, r is the rate of growth, and t is time

    since it grows from 81,500 to 103,200 over a 7 year period, we have:

    103200 = 81500e^{7r}

    solve that for r, that will give you the rate of growth.

    then use it to find what they asked you for, which would be to solve:

    2P_0 =P_0 e^{rt} for t (you will know the value of r at this point, the value of P_0 is immaterial)
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  3. #3
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    answer

    thank you! that really does help
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