Question

3. The half-life of radium-226 is 1600 years. If a sample of radium-226 has an original activity of 200 Bq, what will it’s activity be after 4800 years?

Answer 1

The activity

$$A=A_0 2^{-t/T_{1/2}}=200\times 2^{-4800/1600}=25\:\rm Bq.$$