Question 1196812
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A. Is this a geometric or arithmetic sequence?
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Completely obvious!



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C. What formula can you use to find the radioactive material in the sample at the beginning of the 7th day?
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Initially before any time pass, 500 mg. of the radioactive material.
After one day (or one half-life), {{{500*(1/2)}}};
AFTER two days (or two half-lives), {{{500*(1/2)^2}}};
.
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AFTER some number x days (x number of half-lives), {{{500(1/2)^x}}} {{{mg}}} of material remaining.


The beginning of day 7 is same as the end of day 6, so the amount present than would be  {{{500(1/2)^6}}}.