Question

Sodium-24 has a half-life of 15 hours. If a sample of sodium-24 has an original activity of 500 Bq, what will its activity be after 60 hours?

Answer 1

The activity

$$A=A_0 2^{-t/T_{1/2}}=500\times 2^{-60/15}=31.25\:\rm Bq.$$