c
\(t = n{\tau _{\frac{1}{2}}}\) સમયગાળામાં વિભંજન પામેલા ન્યુક્લિયસોની

સંખ્યા \( = {{\text{N}}_{\text{0}}} - N\,\,\,\) જ્યાં,  \({\text{N}} = {{\text{N}}_{\text{0}}}{\left( {\frac{1}{2}} \right)^n} = {N_0} - {{\text{N}}_{\text{0}}}{\left( {\frac{{\text{1}}}{{\text{2}}}} \right)^n}\)

\( = {N_0}\left( {1 - {{\left( {\frac{1}{2}} \right)}^n}} \right) = 4 \times {10^{16}}\left( {1 - {{\left( {\frac{1}{2}} \right)}^3}} \right)\,\)

(\(\because\) અત્રે  \({{\text{n}} = \frac{{\text{t}}}{{{\tau _{{\text{1/2}}}}}} = \frac{{30}}{{10}}}\) \({ = 3}\))

\( = 4 \times {10^{16}}\left( {1 - \frac{1}{8}} \right) = 4 \times {10^{16}}\left( {\frac{7}{8}} \right) = 3.5 \times {10^{16}}\)