suppose a radioactive isotope has a half- life of 82 years. If we currently have 80kg, how much will be left after 25 years?

Question

suppose a radioactive isotope has a half- life of 82 years.  If we currently have 80kg, how much will be left after 25 years?

anonymous · Answer

that's chemistry, hmm.

is it a first level? second level?

anonymous · Answer

it second level 
If you could help me with it thank you very much 
cause i'm stuck

nowhereman · Answer

halflife of 82 years, means after $$n \cdot 82\; \text{years}$$ there is only an the $$2^n$$'th part left. So after x years there is $$\frac{80\text{kg} }{2^{x/82\;\text{years}}}$$ left.

anonymous · Answer

thank you my teacher told me to put it into the "pert" formula that's why i got confused
could you help me put it into "pert" formula???? thanks

nowhereman · Answer

Sorry, I never heard of such a thing.

anonymous · Answer

it's okay thank you