The half-life of bismuth is 5 days. how much of a 100 gram sample will remain after 20 days? a. 50 grams b. 12.5 grams c. 6.25 grams d. 0 grams

Half-life is the duration needed for a compound to decay into half of its initial weight. In this case, the initial weight is 100gram. The calculation for the final weight should be:

final weight= initial weight * (1/2)^(duration/half-life)
final weight= 100 grams * (1/2)^(20days/5 days)
final weight= 100 grams * (1/2)^(4)
final weight= 100 * 1/16= 100/16 gram= 6.25 grams