To reproduce something at full size (Magnification = 1), the lens-to-film distance would be ( 1 + 1) X focal-length which is 2 X focal-length (known as double extension). For a 55mm lens, this would be 110mm

To reproduce something at twice full size (Magnification = 2, the lens-to-film distance would be ( 2 + 1) X focal length which is 3 X focal-length. For a 55mm lens, this would be 165mm