Finding a half-life if 99.57% remains after one year

AGlas9837

Junior Member
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Jan 23, 2008
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I have a solution to the following problem and just need to know if it is correct: Find the half-life of a radioactive material if after 1 year 99.57% of the initial amount remains. I used an initial amount of 1 gram.

.9957=1e^k(1)
k=ln.9957
k=-.00431 (approx.)
.5=1e^-.00431(1)
t=1/-.00431 ln(1/2)=160.82 years (approx.)
 
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