SOLUTION: A certain radioactive isotope has leaked into a small stream. One hundred days after the leak, 14% of the original amount of the substance remained. Determine the half-life o
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Question 1139086:  A certain radioactive isotope has leaked into a small stream. One hundred days after the leak, 14% of the original amount of the substance remained. Determine the half-life of this radioactive isotope. 
Answer by ankor@dixie-net.com(22740)   (Show Source): You can put this solution on YOUR website!
 A certain radioactive isotope has leaked into a small stream.
 One hundred days after the leak, 14% of the original amount of the substance remained.
 Determine the half-life of this radioactive isotope. 
:
The radio-active decay formula: A = Ao*2^(-t/h), where:
A = amt of substance remains after t time
Ao = initial amt
t = time of decay
h = half-life of substance
:
 Ao = 1,
 A = .14
 t = 100 days
1*2^(-100/h) = .14
using natural logs
ln(2^(-100/h) = ln(.14)
log equiv of exponents
*ln(2) = ln(.14)
:
= 
find the antilog
 = -2.8365
h = 
h = 35.25 days is the half life of the substance
 
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