## Thinking Mathematically (6th Edition)

The equality between the two ratios is known as the proportion. If $a:b\text{ and }c:d$are two ratios, then it will be proportion if $a:b=c:d$. Proportionality between two ratios are determined by symbol$::$, that is if $a:b\text{ and }c:d$are proportional then it can be written as, $a:b::c:d$. Example: consider a numerical example: Two ratios $\frac{4}{9}$ and $\frac{12}{27}$ are taken then The proportionality between the two ratios is$\frac{4}{9}=\frac{12}{27}$.