Radioactive elements is spread over a room, its half life is 30 day, Its activity is 50 times the permissible value. After how many days will it be safe?

Explanation

`N_(0) = 50 N`
`(0.693)/(t_(1//2)) = (2.303)/(t) log_(10) ((N_(0))/(N))`
`(0.693)/(30) = (2.303)/(t) log_(10) ((50N)/(N))`
t = 169.3 days