Background Paragraph: Each radioactive isotope has a characteristic decay time period—the half-life—that is determined by the amount of time needed for half of a sample to decay. This is an exponential decay process that steadily decreases the proportion of the remaining isotope by 50% every half-life. Hence after two half-lives have passed only 25% of the isotope is present, and so forth. 
Story: David was working in his chemistry lab. He selected two isotopes, sample A and sample B. Sample A had longer half-life, but sample B had shorter half-life. After some time he checked sample A when its one half-life had passed. He noted it as sample A1. Then he came back to see it again when two half-lives had passed. He noted it as sample A2.
After certain time, which sample would have less isotopes, sample A or sample B? After certain time, which sample would have more isotopes, sample A or sample B? Which sample would have less isotopes, sample A or sample A1? Which sample would have less isotopes, sample A1 or sample A2? Which sample would have more isotopes, sample A or sample A1? Which sample would have more isotopes, sample A1 or sample A2? Would sample A have less or more isotopes than sample A1? Would sample A1 have less or more isotopes than sample A2? Would sample A1 have less or more isotopes than sample A? Would sample A2 have less or more isotopes than sample A1?