The edge of the cube is 5 cm.
The volume of the cube is (5cm) · (5 cm) · (5 cm) = (5 cm)³ = 125 cm³
The cube has 6 faces.
The area of each face is (5 cm) · (5 cm) = 25 cm²
The area of all 6 faces is (6) · (25 cm²) = 150 cm²
The ratio of its volume to its surface area is
the ratio of
(125 cm³) to (150 cm²)
= 5/6 cm⁻¹ .