The radioactive decay of a certain element can be described

The radioactive decay of a certain element can be described by the equation A = C_r - 0.000278t, where C is the original amount of the element and A is the amount of the element remaining after t years. If 7 milligrams of the element are sealed in a container now, how much of the the element will be in the container after 1224 years? The element amount remaining is A

Solution

A=C e^(-.000276t)

C= 7, t= 1224 yrs

A= 7 e^(-.000276*1224)=5 mg

Therefore after 1224 years,amount left is 5 mg