Answer
$P(all~24~squares~filled~in~correcty)=\frac{1}{2^{24}}$
Work Step by Step
$P(square ~filled~in~correctly)=\frac{1}{2}$
Now, using the Multiplication Rule (see page 282):
$P(all~24~squares~filled~in~correcty)=P(square~1~filled~in~correctly)\times P(square~2~filled~in~correctly)\times P(square~3~filled~in~correctly)\times ...\times P(square~24~filled~in~correctly)=P(square ~filled~in~correctly)^{24}=(\frac{1}{2})^{24}=\frac{1}{2^{24}}$
