d
\({\left( {{{\text{T}}_{1/2}}} \right)_{\text{A}}} = {\left( {{{\text{t}}_{{\text{mean}}}}} \right)_{\text{B}}}\)

\( \Rightarrow \frac{{0.693}}{{{\lambda _A}}} = \frac{1}{{{\lambda _B}}}\) \( \Rightarrow {\lambda _A} = 0.693{\lambda _B}\)

or \(\quad \lambda_{A} < \lambda_{B}\)

Also rate of decay \(=\lambda \mathrm{N}\)

Initially number of atoms \((N)\) of both are

equal but since \(\lambda_{\mathrm{B}}>\lambda_{\mathrm{A}},\) therefore Bwill decay at a faster rate than \(\mathrm{A}\)