SOLUTION: What is the half-life of a radioactive substance if 2.4g decays to .80g in 40 hours?

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Question 364239: What is the half-life of a radioactive substance if 2.4g decays to .80g in 40 hours?
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
N%28t%29=N%5B0%5De%5E%28kt%29
0.8=2.4e%5E%28k%2840%29%29
e%5E%2840k%29=1%2F3
40k=ln%281%2F3%29
k=%281%2F40%29%2Aln%281%2F3%29 or approximately,
k=-0.02747
.
.
.
%281%2F2%29N%5B0%5D=N%5B0%5De%5E%28kt%5BH%5D%29
kt%5BH%5D=ln%281%2F2%29
t%5BH%5D=ln%281%2F2%29%2F%281%2F40%29ln%281%2F3%29
t%5BH%5D=40%28ln%281%2F2%29%2Fln%281%2F3%29%29 or approximately,
highlight%28t%5BH%5D=25.2%29hrs