Posted by **Julie** on Friday, April 20, 2012 at 11:52pm.

A smoke detector contains 0.2 mg of Americium 241 (Am-241), a radioactive element that decays in t years according to the relation m = 0.2(0.5)^(t/432.2). Where m is the mass, in milligrams, remaining after t years.

A) The smoke detector will no longer work when the amount of Am-241 drops below half it's initial value. Is it likely to fail while you own it? Justify your answer.

B) If you buy a smoke detector today, how much of the Am-241 will remain after 50 years?

C) How long will it take for the amount of Am-241 to drop to 0.05 mg?