Nuclear medicine technologists use the Iodine isotope I-131, with a half-life of 8 days,to check thyroid function of patients. After ingesting a tablet containing the iodine, the isotopes collect in a patient's thyroid, and a special camera is used to view its function. Suppose a person ingests a tablet contaiing 9 microcuries of I-131. To the nearest hour, how long will it be until there are only 2.8 microcuries in the person's thyroid?

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1. 2.8=9*e^(-6.93 t/(8*24))

ln (2.8/9)=-6.93 t/182

solve for t in hours. I get about 31 hours

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bobpursley
2. the answers are given, it is 324 hours. im just not sure how to get that.

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3. where did you get -6.93 and 24 from?

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4. m(t)=9x2^(-t/192) 192=24x8

2.8=9x2^(-t/192)
t=192xln(9/2.8)/ln2
t=323.4236495

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