Final answer:
After 260 days, there will be 5 mg of the original 80 mg sample of Strontium-85 remaining.
Step-by-step explanation:
To find out how much of the 80 mg sample of Strontium-85 is left after 260 days, we can use the formula for exponential decay:
A = A0 * (1/2)t/h
Where A is the amount remaining after time t, A0 is the initial amount, t is the elapsed time, and h is the half-life.
Plugging in the values, we get:
A = 80 mg * (1/2)260/65
= 80 mg * (1/16)
= 5 mg
So, after 260 days, there will be 5 mg of the original 80 mg sample of Strontium-85 remaining.