SOLUTION: How old is an artifact that contains 12.5 percent of its original carbon-14?

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Question 481947: How old is an artifact that contains 12.5 percent of its original carbon-14?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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How old is an artifact that contains 12.5 percent of its original carbon-14?
:
The generally accepted value for the half-life of Carbon-14 is 5730 yr
:
Let t = time for 12.5% of the artifact to remain
Let the initial amt = 1
:
1*2^(-t/5730) = .125
use nat logs
-t%2F5730ln(2) = ln(.125)
-t%2F5730 = ln%28.125%29%2Fln%282%29
-t%2F5730 = -3
t = -3 * -5730
t = 17,190 yrs