Krypton-85 is an inert radioactive noble gas with a half-life of approximately 10.76 years. a. Write an exponential function to model this situation and define each variable. ( b. Determine what fraction of a sample of Krypton-85 will remain after 86.08 years. State the answer as an exact fraction value. ( C. Determine how long will it take for a sample of Krypton-85 to decay to 1/64 of its original mass. Round your answer to the nearest hundredth of a year.

I'm getting mixed answers of either 16 or 20. Please advise.

The half-life of a radioactive isotope is 6.02 hours.  25.0 Grams of this isotope is needed for an experiment.  How many grams of the isotope must be ordered if 48 hours pass between the time the isotope is ordered and the start of the experiment?

His case. ewent 5. A radioactive isotope, Selenium, used in the creation of medical images of the pancreas, has a half-life of 119.77 days. If 100 milligrams are given to a patient, how many milligrams are left after 20 days?

A rock contains the radioactive isotope ? − 40 that decays with a half-life of 1.3 ??????? ????? and the radioactive isotope ?? − 87 that decays with a half-life of 48.6 ??????? ?????. The rock is 100 ??????? ????? old. The rock currently has 1000 times as many ?? − 87 atoms as there are ? − 40 atoms. (That is, ??? = 1000 × ??.) When the rock first formed it had ? times as many ?? − 87 atoms as ? − 40 atoms. (That is, ???,0 = ? × ??,0.) What is the value of ??

The number of radioactive nuclei present at the start of an experiment is 4.80 × 10¹5. The number present twenty days later is 6.34 × 10¹4. What is the half-life (in days) of the nuclei? Number i Units

An isotope decays radioactively, so the amount decreases exponentially.  Initially, there were 28 grams of the isotope, but three years later there were only 7 grams.  (You must show work, and simplify your answers, although it's OK to leave e and ln in them.) a.  Give a formula for the amount of the isotope after t years. b.  How much of the isotope will remain, nine years after the start? c.  How long after the start will there be only 14 grams of the isotope left?