Obliczmy sobie przekątna podstawy
[tex] {3}^{2} + {4}^{2} = {x}^{2} \\ 9 + 16 = {x}^{2} \\ {x}^{2} = 25 \\ x = \sqrt{25} \\ x = 5[/tex]
Zatem przekątna prostopadłościanu
[tex] {5}^{2} + {5}^{2} = {y}^{2} \\ 25 + 25 = {y}^{2} \\ {y}^{2} = 50 \\ y = \sqrt{50} \\ y = \sqrt{25 \times 2} \\ \boxed{ \boxed{y = 5 \sqrt{2} }}[/tex]