Advertisement
If you have a new account but are having problems posting or verifying your account, please email us on hello@boards.ie for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact hello@boards.ie

Logs Question - Help!!

  • 22-04-2014 11:57am
    #1
    d1234
    Registered Users, Registered Users 2 Posts: 594 ✭✭✭


    Logs Question:

    The future value , F, of an investment is given by the formula F=P(1 + i)ͭ where P is the present value of the investment, i is the annual rate of interest and t is the time in years. A sum of money, P is invested in a post office account. Using logarithms to find the time taken for the investment to double in value when:

    (i) 5%
    (ii) 7%
    (iii) 10%

    Give your answers correct to the nearest month

    Answers:

    (i) 14 years, 2 months
    (ii) 10 years, 3 months
    (iii) 7 years, 3 months

    Source: Active Maths 4 pg 152


    Any hints anybody?? Thanks!


Comments

  • #2
    JackH14
    Registered Users, Registered Users 2 Posts: 16 ✭JackH14


    Regardless of the interest rate, you apply these first couple of steps.

    If it doubles in value that means F = 2P.

    Therefore, you should get 2P = P(1+i)^t.

    Then divide by P on both sides to get 2 = (1+i)^t

    From there you apply 'ln' (natural log) to both sides of the equation.

    Hope this helps.


  • #3
    d1234
    Registered Users, Registered Users 2 Posts: 594 ✭✭✭d1234


    JackH14 wrote: »
    Regardless of the interest rate, you apply these first couple of steps.

    If it doubles in value that means F = 2P.

    Therefore, you should get 2P = P(1+i)^t.

    Then divide by P on both sides to get 2 = (1+i)^t

    From there you apply 'ln' (natural log) to both sides of the equation.

    Hope this helps.

    Thanks for that!


Advertisement