Radioactivity Questions

In gamma ray emission from a nucleus:

The half-life period of a radioactive element $X$ is same as the mean lifetime of another radioactive element $Y$. Initially they have the same number of atoms. Then:

A radioactive element gets spilled over the floor of a room. Its half-life period is $30\text{days}$. If the initial activity is ten times the permissible value, after how many days will it be safe to enter the room?