calculus

posted by .

assume the half-life of the substance is 31 days and the initial
amount is 183.9 grams.

(a) Fill in the right hand side of the following equation which expresses
the amount A of the substance as a function of time t (the coefficient of t in the exponent should have at least four significant digits):

(b) When will the substance be reduced to 2.4 grams?

(use decimals.)

  • calculus -

    There is not "followiong equation" to fill in.

    Amount left = 183.9*2^(-t/31)

    You don't need 4 sig figs in the exponent in this form if the half life is exactly 31 days.

    (b) When amount left = 2.4,
    2.4/183.9 = 0.01088 = 2^(-t/31)
    -4.5212 = (-t/31)*ln 2 = -0.02236t
    t = 202.2 days

  • calculus -

    the second answer is 194.052 days

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Math/Calculus

    After 5 days, a particular radioactive substance decays to 37% of its original amount. Find the half life of this substance. Is this right?
  2. Calculus-derivatives

    Verify if these are correct answers. 1. The derivative of f(x)=e^2x -e^-2x is f'(x)=2e^2x - 2e^-2x?
  3. Science

    Radioactive substance decays so that after t years, the amount remaining, expressed as a percent of the original amount, is A(t)=100(1.6)^(-t). a) Determine the function A’, which represent the rate of decay of the substance. b) …
  4. calculus

    The rate at which an amount of a radioactive substance decays is modeled by the differential equation dA/dt = kA, where A is the mass in grams, t is the time in years, and k is a constant. Answer the following. a) If a 100-gram sample …
  5. Algebra

    Andrew measures the amount of a very unstable substance to be 100 moles. The half-life of this substance is 3 days (after 3 days, half is gone). Write an exponential function that models this situation where y is the amount of substance …
  6. algebra

    Andrew measures they amount of a very unstable substance to be 100 moles. the half life of this substance is 3 days(after 3 days, half is gone). write an exponential function that models this situation where Y is the amount of substance …
  7. Calculus

    a certain radioactive substance is decaying so that at time t, measured in years, the amount of the substance, in grams, is given by the function f(t)=3e^-3t. What is the rate of decay of the substance after half a year: I first found …
  8. algebra

    A radioactive substance decays according to the formula A=A0e^kt where A0 is the initial amount of substance (in grams) A is the amount of substance(in grams) after t years k is a constant The half-life of the substance is 10 years.If …
  9. Math

    I need help in algebra 1. I have 4 questions, I already answered 3 of them, but I need help with the other Andrew measures the amount of a very unstable substance to be 100 moles. The half-life of this substance is 3 days (after 3 …
  10. College Calculus

    A radioactive substance has a half-life of 27 years. Find an expression for the amount of the substance at time t if 20 grams were present initially.

More Similar Questions