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Math Help - Integration/differentiation

  1. #1
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    Integration/differentiation

    Only just started inegration and differentiation and to top it off, the queston
    has totally thrown me off track, any help through the steps would be greatly appreciated.


    The number of sales, S, in 000's of a phone is given by the formula:
    S=Ae^kt

    where t is time in weeks after the launch. In the week leading to the launch
    3000 phones are ordered (ie when t = 0 then S = 3000)

    In the fifth week (ie at t = 5) 5000 are sold.

    (i) find A and k

    (ii)predict, according to this model, what the phone sales will be after 7
    weeks.

    (iii) How long will it take to reach 20000 per week?

    thankks
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  2. #2
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    S=A.℮^k.t)
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  3. #3
    MHF Contributor Mathstud28's Avatar
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    Pennsylvania
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    Quote Originally Posted by mucky View Post
    Only just started inegration and differentiation and to top it off, the queston
    has totally thrown me off track, any help through the steps would be greatly appreciated.


    The number of sales, S, in 000's of a phone is given by the formula:
    S=Ae^kt

    where t is time in weeks after the launch. In the week leading to the launch
    3000 phones are ordered (ie when t = 0 then S = 3000)

    In the fifth week (ie at t = 5) 5000 are sold.

    (i) find A and k

    (ii)predict, according to this model, what the phone sales will be after 7
    weeks.

    (iii) How long will it take to reach 20000 per week?

    thankks
    It is exponential growth/decay since y=Ce^{kt} we put t=0 when s=3000 to get 3000=Ce^{k\cdot{0}}\Rightarrow{C=3000}..now continue with that until all the variables are found then just plug and chug
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  4. #4
    Newbie
    Joined
    Apr 2008
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    helppp...plz

    Thabks for help but I am still misunderstanding how to find A and k....Please someone help me out
    thankyou........
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