Results 1 to 7 of 7

Math Help - Equation problem (high school level math)

  1. #1
    Newbie
    Joined
    Nov 2012
    From
    Norway
    Posts
    16

    Equation problem (high school level math)

    Hey guys Math newbie here.

    I've been given an assignment, where I am to solve the equation, eg find t:

    Equation problem (high school level math)-math1.jpg

    I've divided by 2,70 on both sides, but after that I'm completely lost. If someone could post a step-by-step solution, I'd be very happy!
    Thank you all

    /Cheers!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor MarkFL's Avatar
    Joined
    Dec 2011
    From
    St. Augustine, FL.
    Posts
    1,988
    Thanks
    734

    Re: Equation problem (high school level math)

    We don't normally post solutions, but will help you to get the solution. You have divided through by 2,70, and so you have:

    \frac{1,5}{2,70}=1-e^{-0,021t}

    I would simplify the left by observing:

    \frac{1,5}{2,70}=\frac{15}{27}=\frac{5}{9} and so we have:

    \frac{5}{9}=1-e^{-0,021t}

    What do you think is a good next step towards isolating the variable t?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Nov 2012
    From
    Norway
    Posts
    16

    Re: Equation problem (high school level math)

    Hey mate,
    Thank you for your respons. I've tried a bit, but I'm still completely lost. I'm sure I'm doing something wrong.
    I would use the rule:

    Equation problem (high school level math)-math2.jpg

    To get:

    Equation problem (high school level math)-math1.jpg
    And then use log to find t, but I know that's wrong :/
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor MarkFL's Avatar
    Joined
    Dec 2011
    From
    St. Augustine, FL.
    Posts
    1,988
    Thanks
    734

    Re: Equation problem (high school level math)

    The next thing you want to do is isolate the exponential term on one side, and everything else on the other.

    Try adding e^{-0,021}-\frac{5}{9} to both sides.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Nov 2012
    From
    Norway
    Posts
    16

    Re: Equation problem (high school level math)

    Hey mate!
    Thanks so much for your help!! I think I got it:

    Equation problem (high school level math)-math3.jpg

    Right? :P
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor MarkFL's Avatar
    Joined
    Dec 2011
    From
    St. Augustine, FL.
    Posts
    1,988
    Thanks
    734

    Re: Equation problem (high school level math)

    I would finish it as:

    e^{-0,021t}=\frac{4}{9}

    e^{0,021t}=\frac{9}{4}

    0,021t=\ln\left(\frac{9}{4} \right)=2\ln\left(\frac{3}{2} \right)

    t=\frac{2000\ln\left(\frac{3}{2} \right)}{21}\approx38.6157245817
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Newbie
    Joined
    Nov 2012
    From
    Norway
    Posts
    16

    Re: Equation problem (high school level math)

    Ah, thank you Yours is closer to the answer giving in my book (actually, the same), so I'll use that from now on!
    Thank you for helping!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. hello I am a math tutor at a high school
    Posted in the New Users Forum
    Replies: 1
    Last Post: March 3rd 2013, 07:08 PM
  2. Help me integrate high school level
    Posted in the Calculus Forum
    Replies: 4
    Last Post: November 14th 2010, 01:47 AM
  3. Two vector questions (high school level)
    Posted in the Calculus Forum
    Replies: 2
    Last Post: July 27th 2008, 08:00 PM
  4. Replies: 8
    Last Post: July 1st 2008, 05:41 PM
  5. Replies: 16
    Last Post: May 3rd 2008, 02:09 PM

Search Tags


/mathhelpforum @mathhelpforum