\(N=\)બાકી રહેલા (અવિભંજીત), \(N_0 =\) પ્રારંભિક
\(N = \frac{{{N_0}}}{{{2^{\frac{t}{{{t_{1/2}}}}}}}}\,\)
\(\, \Rightarrow \,\,\,N = \frac{8}{{{2^{\frac{{5 \times 60}}{{100}}}}}}\,\,\, \Rightarrow \,\,\,\,N = \frac{8}{{{2^3}}}\)
\(= 1\,\,gram\)
$_{92}{U^{238}}{\xrightarrow{\alpha }_B}T{h^A}{\xrightarrow{\beta }_D}P{a^C}{\xrightarrow{E}_{92}}{U^{234}}$