math30
posted by alejandro .
The mass of a radioactive sample is represented in the graph below. The initial mass of 32 mg decays to 8 mg after 21 hours.
1)What is the halflife of the radioactive sample, in minutes?
2)Solve each equation.
a. 4 8x1 = 8
b. 3^(2x5) = 1/27x

8 is 1/4 of 32, so two halflives = 21 hours.
halflife is 10.5 hours
4^(8x1) = (2^2)^(8x1) = 2^(16x2) = 8 = 2^3
so, 16x2 = 3
x = 5/16
assuming 1/27x = (1/27)*x,
3^(2x5) = (3^3)x
(2x5)log3 = 3log3 + logx
(2x2)log3 = logx
nope
assuming a typo, and the x on the right does not belong,
3^(2x5) = 1/27 = 3^3, so
2x5 = 3
x = 1
Respond to this Question
Similar Questions

Chemistry
Which radioactive sample would contain the greatest remaining mass of the radioactive isotope after 10 years? 
CalculusModeling Equations
An unknown radioactive element decays into nonradioactive substances. In 420 days the radioactivity of a sample decreases by 39 percent. 1.What is the halflife of the element? 
physics
Suppose 32000 radioactive nuclei are in a sample. About how many remain after two days if the halflife is 22 hrs? 
Physcis 30
Q1) If there are 100 radioactive atoms with a halflife of 30 seconds, how many radioactive atoms will remain after one halflife (30 seconds)? 
MATH!
The mass of a radioactive substance follows an exponential decay model, with a decay rate of 5% per day. A sample of this radioactive substance was taken six days ago. If the sample has a mass of 3 kg today, find the initial mass of … 
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 100gram sample … 
math
An unknown radioactive element decays into nonradioactive substances. In 100 days the radioactivity of a sample decreases by 64 percent. a)(a) What is the halflife of the element? 
Science Radioactive Dating
Which of the following statements about radioactive dating is true? 
Physics (Inside the atom)
A sample of radioactive isotope I is to be used for medical diagnosis of the kidneys. The isotope has a halflife of 8.0 days, and the sample is required to have an activity of 8 x 10^5 per second at the time it is given to the patient. … 
Engineering Math
An unknown radioactive element decays into nonradioactive substances. In 120 days the radioactivity of a sample decreases by 59 percent. What is the half life of the element?