The half life of radon is 3.8 days. After how long there will be only one twentieth of radon sample left over?

Explanation

Data supplied,
`N = (N_0)/(20), " " N/(N_0) = 1/(2^n) , " " T_(1//2) = 3.8` days
i.e, `1/20 = 1/(2^n) , " " 20 = 2^n`
`log 20 = n log 2`
`n = (log 20)/(log 2) = 4.322`
`t_1 = nT_(1//2) = 3.8 xx 4.322 = 16.42` days.