Question

the half-time life of strontium-85 is 64.84 days. how much of a 40 mg sample would be left after 180 days​

Answer 1

about 5.84 mg

Explanation:

The amount remaining after t days can be written as ...

remaining = initialAmount · (1/2)^(t/(halfLife))

Filling in the given numbers, you have

remaining = (40 mg)·(1/2)^(180/64.84) ≈ 5.84 mg

About 5.84 mg would be left after 180 days.