Question

After 3 days a sample of radon-222 has decayed to 58% of its original amount.

Answer 1

The half-life of the radioactive substance can be determined through teh equation ln 2 = k (t 1/2) where k is equal to ln (1/(1-0.58)) / 3. Hence t 1/2 is equal to 2.40 days. To decay to 10% of the original amount, ln (1/0.90) / ( ln2) / 2.40, time is equal to 0.37 days.