Question

When $t = t_{3/4}\lbrack A\rbrack = \left\lbrack A_{0} \right\rbrack - \frac{3}{4}\left\lbrack A_{0} \right\rbrack = \frac{\left\lbrack A_{0} \right\rbrack}{4}$

Now, $t_{3/4} = \frac{1}{K}.\ln\frac{\left\lbrack A_{0} \right\rbrack}{\left( \frac{\left\lbrack A_{0} \right\rbrack}{4} \right)} = \frac{\ln 4}{K} = \frac{2.303}{K}.\log 4$