$99 \%$ of a radioactive element will decay between

Age of a tree is determined using radio-isotope of

The half-life of radium is about $1600$ years. Of $100\, g$ of radium existing now, $25\, g$ will remain unchanged after ………. $years$

The half life of radioactive Radon is $3.8$ days. The time at the end of which $1/{20^{th}}$ of the Radon sample will remain undecayed is ……….. $day$ (Given ${\log _{10}}e = 0.4343$)

$3.8$ days is the half-life period of a sample. After how many days, the sample will become $\frac{{1}}{{8}} \, th$ of the original substance