Correct. Sketch a diagram as shown below, and use the Pythagorean Theorem.

$\displaystyle{{30}}^{{2}}+{{50}}^{{2}}={{c}}^{{2}}\usepackage{cmbright}\Huge\$

$\displaystyle{900}+{2500}={{c}}^{{2}}\usepackage{cmbright}\Huge\$

$\displaystyle{3400}={{c}}^{{2}}\usepackage{cmbright}\Huge\$

$\displaystyle{58.3}\approx{c}\usepackage{cmbright}\Huge\$