To find side $ l $ use Pythagorean Theorem:
$$ r^2 + h^2 = l^2 $$After substituting $r = 42\, \text{cm}$ and $h = 102.3\, \text{cm}$ we have:
$$ \left( 42\, \text{cm} \right)^{2} + \left( 102.3\, \text{cm} \right)^{2} = l^2 $$ $$ 1764\, \text{cm}^2 + 10465.29\, \text{cm}^2 = l^2 $$ $$ l^2 = 12229.29\, \text{cm}^2 $$ $$ l = \sqrt{ 12229.29\, \text{cm}^2 } $$$$ l = 110.5861\, \text{cm} $$