Question

Doctors can use radioactive chemicals to treat some forms of cancer. The half life of a certain chemical is 5 days. A patient receives 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?

Answer 1

7 millicuries

Explanation:

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.