SOLUTION: Carbon-14 has a half-life of 5,730 years. A fossil is found that has 26% of the carbon-14 found in a living sample. How old is the fossil? (Round your answer to the nearest year.)

Algebra ->  Equations -> SOLUTION: Carbon-14 has a half-life of 5,730 years. A fossil is found that has 26% of the carbon-14 found in a living sample. How old is the fossil? (Round your answer to the nearest year.)      Log On


   



Question 1157177: Carbon-14 has a half-life of 5,730 years. A fossil is found that has 26% of the carbon-14 found in a living sample. How old is the fossil? (Round your answer to the nearest year.)
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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Carbon-14 has a half-life of 5,730 years.
A fossil is found that has 26% of the carbon-14 found in a living sample.
How old is the fossil? (Round your answer to the nearest year.)
:
The radioactive decay formula: A = Ao*2^(-t/h) where:
A = amt after t time
Ao = initial amt
t = time of decay
h = half-life of substance
:
let initial amt = 1, resulting amt = .26
1*2^(t/5730) = .26
use natural logs
ln(2^(-t/5730)) = ln(.26)
log equiv of exponents
-t%2F5730ln(2) = ln(.26)
:
-t%2F5730= ln%28.26%29%2Fln%282%29
using your calc
-t%2F5730 = -1.94341
t = -5730 * -1.94341
t = 11,136 years