SOLUTION: Hello I really need help with this word problem a radioactive isotope decays exponentially. the time it takes for half of the amount to decay is called the isotopes half-life. A

Algebra ->  Exponential-and-logarithmic-functions -> SOLUTION: Hello I really need help with this word problem a radioactive isotope decays exponentially. the time it takes for half of the amount to decay is called the isotopes half-life. A       Log On


   

Question 964524: Hello I really need help with this word problem
a radioactive isotope decays exponentially. the time it takes for half of the amount to decay is called the isotopes half-life. A certain isotope has a half-life of 12 hours. if after 72 hours there are 0.325 mg left, what was the isotopes initial mass?
Answer by josgarithmetic(39614) About Me  (Show Source):
You can put this solution on YOUR website!
Note that 72 hours is six half-lives of 12 hours. You can work the 0.325 mg back upwards according to 0.325%2A2%5E6 for the initial amount. Use this to study how exponential decay equation or functions work.

More typically, you would start with y=pe%5E%28-kt%29 as a general exponential decay equation, and find natural log of both sides, and go through steps.