<PRE><B>Question 79522</B>
The amount of a radioactive tracer remaining ater t days is given by A=Aoe^-0.18t, where Ao is the starting amount at the beginning of the time period. How much should be acquired now to have 40 grams remaining after 3 days?
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40 = Aoe^(-0.18*3)
40 = Ao e^(-0.54)
Ao = 40/e^(-0.54)
Ao = 40/0.582748...
Ao = 68.64 grams (this needs to be the beginning amount)
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cheers,
Stan H.</PRE>