Doctors can use radioactive chemicals to treat some forms of cancer. The half life of a certain chemical is 5 days. A patient re
ceives a treatment of 28 millicuries of the chemical. (A millicurie is a unit of radioactivity.) How much of the chemical remains in the patient 10 days later?
A period of 10 days is 2 times the half-life of 5 days.
In the first 5 days, the amount of the chemical decayed by half from 28 millicuries to 14 millicuries. In the next 5 days, it decayed by half again, from 14 millicuries to 7 millicuries.
10 days later, 7 millicuries of the chemical remains.
