The quotient of two numbers or quantities giving their relative size. The ratio of x to y is written as x : y and is unchanged if both quantities are multiplied or divided by the same quantity. So 2 : 3 is the same as 6 : 9 and 1 : $\frac{3}{2}$. Where a ratio is expressed in the form 1 : a it is called a unitary ratio, and this form makes comparison of ratios much easier.