1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Sequence problem

  1. Oct 3, 2007 #1
    K it's been a while and I cant remember how to figure this problem out without going doing tons of work.

    Estimating that the world population was 0.9 billion in 1798, use this equation to estimate the population (in billions) in the years 1799, 1800, 1801, 1802, and 1900.

    Using the equation y(n+1) = 1.03y(n)

    I got all the years except 1900... I don't remember how to find this out the fast way.. please refresh my memory
  2. jcsd
  3. Oct 3, 2007 #2
    It bottles down to solving the difference equation y(n+1)-1.03y(n)=0
    solving it we get [tex]y[n] = C1 * (1.03)^n[/tex] C1 is a constant
    use initial condition at n =0 we have y(0) = 0.9 (in billions)
    so C1 = 0.9
    then the solution is [tex]y[n] = 0.9 * (1.03)^n[/tex] in billions
    so year 1900 is n= 1900-1798+1 = 103
    Then u get y[103] = 18.9 Billion in the year 1900.
  4. Oct 3, 2007 #3


    User Avatar
    Science Advisor
    Homework Helper

    Don't give the answer, ok? Let the poster find if for him/her self. It takes the fun out of it for them.
  5. Oct 4, 2007 #4
    sorry u are right.... I have avoided this and if u noticed recently I been giving hints and explanations more than solving it to the end (unless required..)
  6. Jan 14, 2011 #5
    not even correct.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook