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Thread: Differential equation

  1. #1
    Feb 2010

    Differential equation

    1. Gainsville had a population of 25000 in 1970 and a population of 30,000 in 1980. Assume that its population will continue to grow exponentially at a constant rate. What population can the Gainsville city planners expect in the year 2010?

    2. Suppose that $1000 is deposited in a savings account that pays 8% annual interest compounded continuously, At what rate (in dollars per year) is it earning interest after 5 year? After 20 year?

    3. In a certain culture of bacteria , the number of bacteria increased sixfold in 10h. Assume natural growth, how long did it take for their number to double?

    4. Let f(x)= 3x + 4, x(y)= y-9, and y(z)= z^2 + 1. Implicitly, if z=3, what does f equal to?

    5. The salt KNO3 dissolves in methanol at a rate x'(t)= (0.8)x -(0.004)x, where x is the number of grams of salt in solution after t seconds. Let x(0)= 50 . What x is the value of t such that x(t)= 100 (report to the nearest hundredth of a second)?
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  2. #2
    Flow Master
    mr fantastic's Avatar
    Dec 2007
    1. Please read the forum descriptions more carefully, become more familiar with the different available subforums and then post questions in the appropriate subforum. The subject matter of some of these questions better belongs in other subforums.

    2. Please don't post more than two questions in a thread. Otherwise the thread can get convoluted and difficult to follow. It is better for forum organization and better for you to get your questions answered in a more timely manner if you start new threads as necessary for remaining questions. eg. If you have five questions, post two of them in two threads and start a new thread for the remaining one etc.

    And if the question has more than two parts to it, it is best to post only that question and its parts in the thread and start a new thread for other questions.

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