Given $A_{0}=10\,A$
$\lambda=\frac{0.693}{t_{1 / 2}}=\frac{0.693}{30}$
$t_{1 / 2}=\frac{2.303}{\lambda} \log \frac{A_{0}}{A}$
$=\frac{2.303}{0.693 / 30} \log \frac{10\,A}{A}$
$=\frac{2.303 \times 30}{0.693} \times \log 10$
$=100$ days .
(આપેલ છે: $\left. R =8.314\, J\, mol ^{-1} K ^{-1}\right)$