The length of DE in the cuboid is 18.7 cm to 1 d.p.
To find the length of DE using Pythagoras' theorem, we need to know the lengths of two of the other sides of the triangle. We can see that triangle FHG is a right-angled triangle, with FH = 5 cm and GH = 18 cm. Therefore, we can use Pythagoras' theorem to find the length of FG:
DE² = EH² + HD²
DE² = 5² + 18²
DE² = 25 + 324
DE = √349
DE ≈ 18.7 cm
Therefore, the length of DE in the cuboid is 18.7 cm to 1 d.p.