SOLUTION: A radioactive substance has a halflife of 120 years. If 200mg of substance was present, how much of the substance remains after 340 years?

Algebra ->  Exponential-and-logarithmic-functions -> SOLUTION: A radioactive substance has a halflife of 120 years. If 200mg of substance was present, how much of the substance remains after 340 years?      Log On


   

Question 841973: A radioactive substance has a halflife of 120 years. If 200mg of substance was present, how much of the substance remains after 340 years?
Answer by josgarithmetic(39621) About Me  (Show Source):
You can put this solution on YOUR website!
Decay Equation in general, A=Ie%5E%28-kt%29.
A = amount after time t
I = initial amount when t=0
k = a constant
At half-life, %281%2F2%29=e%5E%28-kt%29 and you would want to find k for a given or known t.
ln%281%2F2%29=-kt
k=-%28ln%281%2F2%29%29%2Ft

You are given that t=120 for the half life and so you can calculate and find the value for k.