A sample of a radioactive isotope had an initial mass of 480 mg in the year 2009 and decays exponentially over time. A measureme
nt in the year 2011 found that the sample's mass had decayed to 390 mg. What would be the expected mass of the sample in the year 2016, to the nearest whole number?
If you go from 2009 to 2011 and decayed 390 mg, you divide that by two to see how much it decays in one year. After you get that, you multiple 195 by 5 and get 975. your initial value is 480, so you would add 975 and 480 to get the answer 1445 mg. I am only in the 7th grade, so I could be wrong but it looks like a simple slope problem and I feel pretty confident about my answer.
