Scale factor causes enlargement or reduction of the original image.
A scale factor greater than 1 causes enlargement while a scale factor lesser than 1 causes reduction.
From the information given, traingle A was scaled by a factor of 1/2 to give triangle B
This means that if the side length of A is 6, the side length of B would be 6 * 1/2 = 3
Therefore, the side length of triangle A is 2 times the side length of triangle B.