A [b]ratio [/b]is a quotient of two quantities. They are useful to [b]compare [/b]how two magnitudes relate (it quantifies such relation).[br]The [b]ratio [/b]between two numbers a and b is often written as:[list][*] [math]a[/math] to [math]b[/math], or[/*][*] [math]a:b[/math], or[/*][*] [math]\frac{a}{b}[/math].[/*][/list]