$1.5\,\, \times \,\,1{0^{ - 2}}\, = \,\,K\,\, \times \,\,0.5$
$K\,\, = \,\,3\,\, \times \,\,{10^{ - 2}}\,{\min ^{ - 1}}$
${t_{1/2}}\,\, = \,\,\frac{{0.693}}{K}\, = \,\,\frac{{0.693}}{{3\,\, \times \,\,{{10}^{ - 2}}}}\,\, = \,\,23.1\,\,\min .$
(આપેલ : $\ln 10=2.303\,\log 2=0.3010$ )