The amount of a sample remaining after t days is given by the equation P t A 3 where A is the initial amount of the sample and h is the half life in days of the substance A scientist has a 10 mg sample of a radioactive isotope The isotope has a half life of 8 days After 16 days how much of the radioactive isotope remains 2 0 mg 7 1 mg 5 7 mg 2 5 mg