After $45$ days, a radioactive substance has decayed in $\backslash (55\mathrm{.}1\backslash \%\backslash )$ of its original amount. After an additional $45$ days, what percent of its original amount will it have decayed to$?$

$27\mathrm{.}6\backslash \%$

$30\mathrm{.}4\backslash \%$

$24\mathrm{.}7\backslash \%$

$55\mathrm{.}1\backslash \%$