Question 1196812
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A. Is this a geometric or arithmetic sequence?<br>
The amount of radioactive material remaining gets multiplied by 1/2 each day.  That should make the answer obvious, if you know the definitions of arithmetic and geometric sequences.<br>
B. Does it make a difference if you calculate the {{{cross(half-life)}}} amount remaining at the beginning or end of the day? Explain.<br>
From the beginning of any day to the end of the day, the amount remaining gets cut in half; of course it makes a difference.<br>
C. What formula can you use to find the radioactive material in the sample at the beginning of the 7th day?<br>
The beginning of the 7th day is the end of the 6th day.  Assuming the amount is 500mg at the beginning of the first day (the problem doesn't say so...), the formula for the amount remaining at the beginning of the 7th day is {{{500((1/2)^6)}}}.<br>