Determine the fraction of an original sample of Co-60 that will remain unchanged after 26.35 years in storage

A radioactive Cobalt 60 has a half life of 5.25 years.

Therefore; the fraction that will remain after 26.35 years will be;

26.35 years

New mass = original mass * (1/2) ^n

Where n is the number of half lives

n = 26.35/5.25

= 5.019

If the original mass is 1 whole, then the new mass would be;

= 1 * (1/2) ^5.019

= 0.03084

≈ 0.03 or 3/100

Therefore, an approximate fraction of 3/100 will remain