The diagonal of a rectangle forms a right triangle with the two dimensions of the rectangle. If xx is the diagonal (hypotenuse), then by Pythagorean Theorem,

\(\displaystyle{24}^{{2}}+{18}^{{2}}={x}^{{2}}\)

\(\displaystyle{576}+{324}={x}^{{2}}\)

\(\displaystyle{900}={x}^{{2}}\)

\(\displaystyle{x}=√{900}\)

PSKx=30→30 inches

\(\displaystyle{24}^{{2}}+{18}^{{2}}={x}^{{2}}\)

\(\displaystyle{576}+{324}={x}^{{2}}\)

\(\displaystyle{900}={x}^{{2}}\)

\(\displaystyle{x}=√{900}\)

PSKx=30→30 inches