What is the scale factor of triangle A to triangle D.

When two shapes are similar, their corresponding angles will be the same.  The angles are the same because the shape is still the same.  You can tell from the order of the similarity statement which angles match up.  In the example, angles A and D are the same (both letters are in written first), angles B and E are the same (both letters are written in the middle), and C and F are the same

Step-by-step explanation:

Similar triangles can be different sizes, so the lengths of the corresponding sides are not necessarily the same, but they are proportional.  This means that the ratios of the corresponding sides are equal.

people went from manufacturing one object at a time by hand to manufacturing many objects in factories