The half-life of a radioactive isotope is 5.0 days5.0\text{ days}5.0 days.
A sample of this material contains 80 million80\text{ million}80 million radioactive nuclei.
How many of these radioactive nuclei remain undecayed after 15 days15\text{ days}15 days?
5.0 million5.0\text{ million}5.0 million
10 million10\text{ million}10 million
20 million20\text{ million}20 million
40 million40\text{ million}40 million
144 exam-style questions on CIE IGCSE Physics 5.2.4a Half-life. Each one has a worked solution and a mark scheme showing where the marks go.