The half life of radioactive radon is 3.8 days. Find the time during which `1/20` remain undecayed.

The half life of a radioactive substance is 4.2 days. Find the time during which 1/8" of the sample will remain undecayed.

The half-life of Radon is 3.8 days. Define half-life.

The half-life of Radon is 3.8 days. Calculate how much of 15 mg of Radon will remain after 14.2 days.

The half-life period of a radioactive material is 5 hours. In how much time 15/16 of the material will decay?