Answer to Question #113369 in Physics for Cris

Question

How much of a 32 gram sample of I-131 remains after 48 days ?(half life of I-131 is 8 days )

Answer 1

The radioactive decay equation says

$$m(t)=m_0 2^{-t/t_{1/2}}$$

Hence, we get

$$m=(32\:\rm g) 2^{-48/8}=0.5\:\rm g$$