Representative Fraction:

It is a linear ratio that is the ratio of the length of a drawing to the real length of an object. The numerator and the denominator should be in the same units; thus the Representative Fraction or like RF is a number merely.

RF  = Length of drawing/Actual length of object

Example

If a length of 5 m on the ground is presented via 5 cm line on a drawing, so the RF of the scale

= 5 cm/(5 × 100 cm)

=   1/100

It is forever customary to present RF like a fraction 1 on something.