A radioactive sample has an initial activity of 80 Bq. After 3 half-lives, what is the remaining activity of the sample? Use the fusion core context to keep Half-lives and the random nature of radioactive decay distinct from nearby atomic and nuclear radiation ideas.

10 Bq In this fusion core context, the answer must stay anchored to Half-lives and the random nature of radioactive decay and the learning objective: Calculate the number of half-lives that have passed from a change in activity or count rate..

10 Bq is correct because the worked solution uses remaining = initial / 2^n and substitutes the values from the question. This keeps activity, count rate, atomic number, mass number and neutron count distinct for Atomic structure. Use the fusion core context to keep Half-lives and the random nature of radioactive decay distinct from nearby atomic and nuclear radiation ideas. This avoids collapsing the idea into nearby concepts such as isotope notation, count rate, half-life, alpha, beta, gamma, contamination, irradiation, fission or fusion.