1. If the half-life of a radioactive sample is 10 years, then it should take _____ years for the sample to decay completely.
(a) 10.
(b) 20.
(c) 40.
(d) Cannot be determined.
2. A sample's half-life is 1 day. What fraction of the original sample will have decayed after 3 days?
(a) 1/8,
(b) 1/4,
(c) 1/2,
(d) 3/4,
(e) 7/8.
(f) All of it.