if PQR~ STU, what is the scale factor of PQRto STU?

we can see the scaling factor as a fraction
[tex]\frac{4}{20}[/tex]This fraction relates the value of STU with respect to PQR
simplify the fraction
[tex]\frac{\frac{4}{4}}{\frac{20}{4}}=\frac{1}{5}[/tex]