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

Two radioactive isotopes A and B of atomic mass X and Y are mixed in equal amount by mass. After 20 days, their mass ratio is found to be 1: 4. Half life of 'A' is 1 day. What will be the half life of B ?