Question

The rectangular prism shown has a length of 12 cm, a width of 12 cm, and a height of 8 cm. Find the length of the inner diagonal (AD) of the prism. Note that (AD) is the hypotenuse of right triangle ACD. (Round your answer to the nearest hundredth.)

Answer 1

This is simply where you apply the Pythagorean equation twice. 

Find the base hypotenuse by Pythagorean equation. 
h² = 12² + 12² = 288 

Then find the inner diagonal using that and the height. 
D² = h² + 8² 
D² = 288 + 64 
D = √352 
simplify to 4√22 
appx 18.76cm

Answer 2

I hope this helps you