SOLUTION: After 13 years, 2.1 pounds of radioactive material remains from a 7 pound sample. What is the half-life of this material?

Question 187395: After 13 years, 2.1 pounds of radioactive material remains from a 7 pound sample. What is the half-life of this material?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
After 13 years, 2.1 pounds of radioactive material remains from a 7 pound sample. What is the half-life of this material?
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A(t) = A(0)(1/2)^(13/h)t
2.1 = 7 (1/2)^(13/h)t
0.3 = (1/2)^(13/h)
Take the log to get:
(13/h)log(0.5) = log(0.3)
(13/h) = [log(0.3)]/[log(0.5)]
13/h = 1.7370
h = 13/1.7370
h = 7.4843 years (this is the half-life of the material)
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Cheers,
Stan H.
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