math

Suppose y , the number of cases of a disease, is reduced by 11% per year.

(a) If there are initially 10,000 cases, express y as a function of t , the number of years elapsed.

(b) How many cases will there be 6 years from now?

(c) How long does it take to reduce the number of cases to 1000?

asked by George
  1. a) y =10000(0.11)^t
    b) y = 10000(0.11)^6 and you solve it
    c) 1000 = 10000(0.11)^t and I would divide both sides by 10000 first then either uses exponents or take the log of both sides to solve

    posted by MsPi_3.14159265
  2. it is reduced by .11/yr so multiply by 0.89^t

    posted by Damon
  3. It is reduced by 11% leaving 89%

    so y = 10000(.89)^t

    b) y = 10000(.89)^6

    c)
    10000(.89)^t = 1000
    .89^t = .1
    t log .89 = log .1
    t = -1/-.0506099.. = appr 19.76 years

    posted by Reiny
  4. Thanks math gang! Time for a cup of afternoon tea. I was doing the math in my head and .89 didn't feel just right. LOL! Thanks again for the correction : )

    posted by MsPi_3.14159265

Respond to this Question

First Name

Your Response

Similar Questions

  1. math

    The number of cases for a disease has reduced by half every 10 years: 1970 - 21,168 1980 - 10,584 1990 - 5,292 Assume N is the number of reported cases t years after 1970. Which is a good model for N(t)? a) 21,168 (2)^t b) 21,168
  2. Probability

    A screening test for a disease shows a positive test result in 95% of all cases when the disease is actually present and in 20% of all cases when it is not. When the test was administered to a large number of people, 21.5% of the
  3. Epidemiology

    How do you calculate the disease frequency rate in these problems 1. The cumulative incidence rate in a population of 100,000 people where 9 new cases of disease were reported within 1 year 2. The prevalence of a chronic disease
  4. Health

    Does prevalence of disease increase as chronic disease increases. Prevalence is total no. of cases/total no. of risk factors of disease in the population over a period of time.
  5. biostatistics

    Seventeen people has been exposed to a particular disease. Each one independently has a 40% chance of contracting the disease. A hospital has the capacity to handle 10 cases of the disease. What is the probability that the
  6. psychology

    why might recent research have indicated an increase in the total number of cases os alzheimer's disease in the past few yearss
  7. economics

    Suppose the president is attempting to decide whether the federal gov should spend more research to find a cure for heart disease. How should policy makers determine the amount of money that should be allocated for research curing
  8. Calculus

    The number of people expected to have a disease in t years is given by y(t) = A.3^(t/a) (i) If now (year 2016) the number of people having the disease is 1000, find the value of A. (ii) How many people are expected to have the
  9. Calculus

    The number of people expected to have a disease in t years is given by y(t) = A.3^(t/a) (i) If now (year 2016) the number of people having the disease is 1000, find the value of A. (ii) How many people are expected to have the
  10. Calculus

    The number of people expected to have a disease in t years is given by y(t)=A•3^(t/4) i) if now year(2016) the number of people having disease is 1000, find the value of A? ii) how many people expected to have the disease in

More Similar Questions