please help me!!

Question

Bandages can be sterilized by exposure to gamma radiation from cobalt-60, which has a half-life of 5.27 y. How much of a 10.6-mg sample of cobalt-60 is left after one half-life? 

Answer 1

Fraction remaining = 0.5ⁿ where n = number of half lives elapsed

fraction left = 0.5¹ = 0.5

So 50% is left and that is equal to 5.3 mg