Question

Iodine-125 has a half-life of about 60 days. How many milligrams of a 500 mg sample will remain after 300 days?

Answer 1

As stated correctly in the answer above it is in fact 15.625

Answer 2

60 x 5 = 300 days

So five half-lifes = 300 days

Starting amount = 500mg

Amount after 1st half-life = 250 mg

Amount after 2nd half-life = 125 mg

Amount after 3rd half-life = 62.5 mg

Amount after 4th half-life = 31.25 mg

Amount after 5th half-life = 15.625 mg

Hence after 300 days, the amount of iodine-125 will be 15.625 mg out of 500 mg.