Question

The half-life of I-137 is 8.07 days. If 25 grams are left after 40.35 days, how many grams were in the original sample?

Answer 1

40.35 da / 8.7 da/half-life = 5 half lives

The sample has gone thru 5 half lives

2^5 = 32 only 1/32 of the original amount is left

25 g * 32 = 800 g present in the original sample