The answer is a 1/2 gram or 0.5 grams. After 8 days, there will be 4 grams. After 16 days, there will be 2 grams. After 24 days, there will be 1 gram. And after 32 days, there will be a 1/2 gram or 0.5 grams. The formula is (1/2)^n = fraction remaining where n is the number of half-lives. In this case, n=4, since 32/8=4. The formula gives us (1/2)^4=1/16 1/16 of 8 grams (the starting amount) is 1/2 gram or 0.5 grams