Question 119507
{{{1 cm :1 km}}}

About metric system:

{{{1cm}}} is {{{(1/100)m}}}….or {{{1m=100cm}}}

{{{1m}}} is {{{(1/1000)km}}}….or {{{1km=1000m}}}

Another common example of a ratio is a map scale.

In your example map scale might be {{{1:100000}}}.

In this case it means that {{{1cm}}} on the map represents {{{100 000cm}}} in "real-life".

{{{100000 cm = 100000 cm /100 =1000m/1000 = 1km}}} 

so {{{1cm}}} on the map represents {{{1 km}}}. 

or

{{{1 cm :1 km = 1 cm : 100000 cm }}}