A sample of a radioactive isotope had an initial mass of 480 mg in the year 2009 and decays exponentially over time. A measurement 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?

The weight of a radioactive isotope was 96 grams at the start of an experiment. after one hour, the weight of the isotope was half of its initial weight. after two hours, the weight of the isotope was half of its weight the previous hour. if this pattern continues, which of the following graphs represents the weight of the radioactive isotope over time? a. graph w b. graph x c. graph y d. graph z