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anonymous
 5 years ago
A certain radioactive isotope has a halflife of approximately 900 years. How many years would be required for a given amount of this isotope to decay to 70% of that amount?
anonymous
 5 years ago
A certain radioactive isotope has a halflife of approximately 900 years. How many years would be required for a given amount of this isotope to decay to 70% of that amount?

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anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0can you continue and show work

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0\[e^{900r}=1/2\] 900 r ln e= ln 1/2 900 r= ln 1/2

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0write the formula as \[Q = Q_0(\frac{1}{2})^{\frac{t}{900}}\]

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0set \[.7=(\frac{1}{2})^{\frac{t}{900}}\] and solve for t

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0\[ln(.7)=\frac{t}{900}\times ln(\frac{1}{2})\]

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0\[t=\frac{900ln(.7)}{ln(\frac{1}{2})}\]

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0if you want to do it the first way using \[Q=Q_0e^{rt}\] then first you have to solve for r, then set the result equal to 1/2 and solve for t. it will work and you will get the same answer, but it is extra work

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0imaram started the problem for you but you still have to solve for r, replace it in the equation, set = to 1/2 and then solve for t.
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