
To find median $ m $ use formula:
$$ m = \frac{ a + b } { 2 } $$After substituting $a = 13\, \text{cm}$ and $b = 9\, \text{cm}$ we have:
$$ m = \frac{ 13\, \text{cm} + 9\, \text{cm} } { 2 } $$ $$ m = \frac{ 22\, \text{cm} } { 2 } $$ $$ m = 11\, \text{cm} $$