what is the sing of proprotion ?

Dear student,
Here is the answer to your asked query:

Sign of proportion is ::
If ratios are equal they are said to be in same proportion.
$$\begin{gathered} 1:2=\frac{1}{2} \\ 3:6=\frac{3}{6}=\frac{\cancel{3}1}{\cancel{6}2}=\frac{1}{2} \\ \mathrm{Here} \mathrm{both} \mathrm{ratios} \mathrm{are} \mathrm{equal}. \mathrm{so} \mathrm{they} \mathrm{are} \mathrm{in} \mathrm{proportion}. \\ \mathrm{so} \mathrm{we} \mathrm{can} \mathrm{write} \mathrm{it} \mathrm{as}; 1:2::3:6 , \mathrm{where} :: \mathrm{represents} \mathrm{proportion}. \end{gathered}$$
Regards