Question

A right rectangular prism is shown.

Answer 1

So what you are looking for is the hypotenuse of the triangle DCF. 

We know DC is 3cm, so we need CF.

BC and CF and CF create a right triangle. 

Using Pythagorean Theorem, CF is about 10.2

Now using Pythagorean Theorem again, 3^2 +10.2^2=113

The sqaureroot of that is 10.6. So 10.6 is your answer