How Well do Dancing's Derek Hough and Nastia Liukin know each other?

Nastia Liukin and Derek Hough have been Dancing with the Stars partners for two months, which is plenty of time to get to know one another... or at least fire up Google. We dropped by the pair's tango rehearsal last week to put to them to the test. How did they do? Well, not to add insult to Hough's literal injury, but numbers still aren't his strong suit. TV Guide's official YouTube channel brings you behind-the-scenes access to your favorite shows and interviews with your favorite celebs! For more news, videos and photos click HERE: http://bit.ly/1qAossx Click HERE to SUBSCRIBE to the TV Guide channel: http://bit.ly/11yINCm TV Guide on Facebook: http://on.fb.me/1HqOzab TV Guide on Twitter: http://bit.ly/11GJx9o TV Guide on Google+: http://bit.ly/1BQPtN3