Suppose the isotope your skittles® represented was uranium-238 and the trials represent the number of half-lives. how old was the sample at the end of your tests? use table 1 in the introduction to help you answer this question. include your calculations. 3. if 1/8 of a radioactive element remains after 600 years, what is that element's half-life? 4. identify and describe similarities and differences between this experiment and radioactive decay in nature.