Please help!

Can someone help me out with this trick math question by showing their work. A cube measures 3 yards on each side. How long is the diagonal that connects two opposite corners of the cube?
Thanks very much in advance.

do pathagorian theorom...wat ur looking for is the hypotinuse

Complete with pictures. :-)

http://mathcentral.uregina.ca/QQ/database/QQ.09.04/brett1.html