The side length of square ABCD is 3 units
The side length of square A'B'C'D' is 1 unit
The scale factor is by what number we multiply the side length of ABCD to get A'B'C'D'.
Let that be "x", so we can say >>>
3 times "what number" to get 1
or,
3 times x to get 1
In equation, that is:

Solving for x:

Hence,
The scale factor is
