A radioactive element has half life period of 30 days. How much of it will be left after 90 days?

Explanation

Total time = 90 days
Half life `(t_(1//2)) = 30` days
so, `90 = n xx 30`
n = 3
Thus, quanitity left after three half life periods
`= ((1)/(2))^(3) N_(0)` [`N_(0)` = original amount]
`= (1)/(8) xx N_(0) = (1)/(8) N_(0)`