Results 1 to 2 of 2

Thread: serium

  1. #1
    Member
    Joined
    Apr 2010
    From
    dfsdfdf
    Posts
    160

    serium

    Dear Sir
    I would be grateful if you can help me to solve the the below questions
    I managed to get the answer to part (a) but cannot get the time 11.16 minutes in part b

    thanks
    Kingsman

    I
    Attached Thumbnails Attached Thumbnails serium-de1.bmp  
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    5
    Quote Originally Posted by kingman View Post
    Dear Sir
    I would be grateful if you can help me to solve the the below questions
    I managed to get the answer to part (a) but cannot get the time 11.16 minutes in part b

    thanks
    Kingsman

    I
    This is a seperable differential equation with solution:

    $\displaystyle x=10+Ae^{-t/50}$

    As $\displaystyle x(0)=20$, we have $\displaystyle A=10$

    so:

    $\displaystyle x=10(1+e^{-t/50})$

    To find when $\displaystyle x(t)=18$ we solve:

    $\displaystyle 10+Ae^{-t/50}=18$

    which has solution:

    $\displaystyle t=-50 \ln(0.8)=11.16$ minutes (rounded to two places of decimal)

    CB
    Follow Math Help Forum on Facebook and Google+

Search Tags


/mathhelpforum @mathhelpforum