1. The problem statement, all variables and given/known data If a patient is given a radioactive isotope which has a half-life of six days and a biological half-life of ten days, what is the effective half-life for the isotope. 2. Relevant equations I know the formula for half-life calculations is T1/2 = 0.693/k 3. The attempt at a solution I don't know where to start with this. My tutor just briefly went over it. It was a question on a past paper so I just want it covered in case it comes up in my exams. Any help I'd be grateful. Thanks.