SOLUTION: If 10 g of a radioactive substance are present initially and 9 yr later only 5 g​ remain, how much of the substance will be present after 14 ​yr?

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Question 1128806: If 10 g of a radioactive substance are present initially and 9 yr later only 5 g​ remain, how much of the substance will be present after 14 ​yr?

Answer by josgarithmetic(39621) About Me  (Show Source):
You can put this solution on YOUR website!
After 14 years, from what?

y=10%2Ab%5Ex
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10%2Ab%5E9=5
b%5E9=1%2F2
log%28%28b%5E9%29%29=log%28%281%2F2%29%29
9%2Alog%28%28b%29%29=log%28%281%2F2%29%29
log%28%28b%29%29=%281%2F9%29%2Alog%28%281%2F2%29%29
log%28%28b%29%29=log%28%28%280.5%29%5E%281%2F9%29%29%29
b=%280.5%29%5E%281%2F9%29

b=0.9259

highlight%28y=10%2A%280.9259%29%5Ex%29--------the model to use.



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this is not the only exponential model possible.
notice that the given data is for half-life.