$P\left(MJMJM\right)=\frac{3}{5}\cdot\frac{2}{4}\cdot\frac{2}{3}\cdot\frac{1}{2}\cdot\frac{1}{1}$

$=0{,}1=10\,\%$

$P(MMMJJ)=\frac35\cdot\frac24\cdot\frac13\cdot\frac22\cdot\frac11=0{,}1=10\,\%$

$P(JJMMM) = \frac25\cdot\frac14\cdot\frac33\cdot\frac22\cdot\frac11=0{,}1=10\,\%$

$P(JMMMJ)=\frac25\cdot\frac34\cdot\frac23\cdot\frac12\cdot\frac11=0{,}1=10\,\%$

$\Rightarrow P(\text{3 Mädchen hintereinander})= 10\,\%+10\,\%+10\,\%=30\,\%$