Results 1 to 4 of 4

Math Help - Exponential and logarithmic Functions help

  1. #1
    Newbie
    Joined
    Apr 2009
    Posts
    20

    Exponential and logarithmic Functions help

    I have the equation y = 15^x which determines the population and x is how many days.

    Determine to the nearest day when the population will reach 600.

    How do I figure out the above without just guess and check?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Newbie
    Joined
    May 2009
    Posts
    21
    You can set y=600 and take logarithms on both side to solve for x.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,236
    Thanks
    29
    Quote Originally Posted by olen12 View Post
    I have the equation y = 15^x which determines the population and x is how many days.

    Determine to the nearest day when the population will reach 600.

    How do I figure out the above without just guess and check?
    guess and check will work fine unless your calculator can calculate base 15, then...

    x= log_{15}(600)
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor

    Joined
    Apr 2005
    Posts
    16,449
    Thanks
    1864
    Quote Originally Posted by pickslides View Post
    guess and check will work fine unless your calculator can calculate base 15, then...

    x= log_{15}(600)
    Even if your calculator does NOT have a logarithm, base 15, You can do 600= 15^x using log base 10 (common log) [tex]log_{10} 600= log_{10}(15^x)= x log_{10}(15)[tex] so x= \frac{log_{10}(600)}{log_{10}(15)}.

    Or with the natural logarithm key, "ln", ln(600)= ln(15^x)= xln(15) so x= \frac{ln(600)}{ln(15)}.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Exponential and Logarithmic Functions
    Posted in the Algebra Forum
    Replies: 2
    Last Post: December 12th 2010, 05:42 PM
  2. Exponential and Logarithmic Functions
    Posted in the Algebra Forum
    Replies: 3
    Last Post: February 23rd 2010, 03:04 PM
  3. exponential & logarithmic functions
    Posted in the Calculators Forum
    Replies: 4
    Last Post: November 27th 2009, 07:59 PM
  4. Logarithmic and Exponential Functions?
    Posted in the Calculus Forum
    Replies: 1
    Last Post: November 23rd 2008, 03:00 PM
  5. exponential and logarithmic functions
    Posted in the Algebra Forum
    Replies: 3
    Last Post: July 29th 2008, 10:58 PM

Search Tags


/mathhelpforum @mathhelpforum