How long will it take a sample of radioactive substance to decay to half of its original amount, if it decays according to the function A(t) = 400e -.169t, where t is the time in years? Round your answer to the nearest hundredth year.

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