The half life of Unobtainium 280 is 15 minutes. If I have 1600 grams of Unbtainium 280 to begin with, how many minutes will elapse such that I have 25 grams of it left?

Strontium-82 has a half-life of 25.5 days. If you start with 100.0 g on January 1st 2018, approximately how much would you have left over on January 1st, 2019?

Americium-241 is widely used in smoke detectors. Calculate the amount of americium-241 consumed in a smoke detector (initially containing 2.1000 µg of Am), in micrograms, that has been used for 1.000 year if the half-life is 433 years.

Strontium-90 has a half life of 28 years. If a 5.31 mg sample was stored for 112 years, what mass of Sr-90 would remain?

Americium-241 is widely used in smoke detectors. Calculate the amount of americium-241 consumed in a smoke detector (initially containing 3.60 µg of Am), in micrograms, that has been used for one year if the half-life is 433 years.