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posted by  confusedbyphysics on 4/28/2008 8:44:52 PM  |  status: Closed  

Help. My answer is incorrect!

Course Textbook Chapter Problem
Calculus Based Physics Physics (7th) by Cutnell, Johnson 31 34P
Question Details:
A certain radioisotope has a half-life of 11.9 days. What fraction of an initial sample of this isotope remains after 43.3 days?
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posted by Sarah21 on 4/28/2008 8:52:21 PM  |  status: Live
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confusedbyphysics's comment:
"Thank you so much. I understand my error!"
Response Details:
 
ln(a) = -kt + ln(ao)         t1/2= .693/ 11.9    t1/2= .058235
ln(a) = - (.058235)(43.3) + ln (10)       the ten is just a sample to find our ratio
a=0.803
 
0.803/10   = 0.08
 
This is roughly 8/100 or 2/25 of its initial value
Hope this helps!  Please take the time to rate my answer accordingly.  Thanks! 
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