How do you find the length inside a cube

Solution:

We have: In the attached image, observe rectangle triangle ΔBAD
Use the Pythagorean Theorem:
BD = √(AB² + AD²)
BD = √(2² + 4²)
BD = √(4 + 16)
BD = √20

In the attached image, observe rectangle triangle ΔBDH
Use the Pythagorean Theorem:
BH = √(BD² + DH²)
BH = √(√20² + 5²)
BH = √(20 + 25)
BH = √45
BH = √(9 × 5)
BH = √9 × √ 5
BH = 3√5
BH = 3 × 2.24

BH = 6.72 cm

820,000 is the answr