If line EF was dilated by a scale of 1/2 from the origin to get line E'F', then if line E'F' is dilated by a scale of 2 from the origin, EF is obtained. Also, the length of EF is double than the length of E'F'.
Dilation by a scale of 2 from the origin transforms point (x,y) into (2*x, 2*y)