Question 118973
{{{1*cm/8km=x*cm/16km}}}


When you set up your proportion, make sure that similar quatities are in the numerators and denominators.  Here, the numerators are 1 centimeter and x centimeters, while the denominators are 8 kilometers and 16 kilometers.


Now cross-multiply and solve:


{{{8x=1*16}}}
{{{x=2}}}


And remembering that x was expressed in centimeters in the original equation, so the answer is 2 cm.