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 of Radon is 3.8 days. Define half-life.

Half-life of iodine (atomic mass 125) is 60 days. Calculate the present of radioactivity remain after 120 days.

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