The ratio is the relationship of two numbers.
For example you have 2 flashlights and 5 batteries. To compare the ratio between the flashlights and the batteries we divide the set of flashlights with the set of batteries.
The ratio is 2 to 5 or 2:5 or 2/5. All these describe the ratio in different forms of fractions. The ratio can consequently be expressed as fractions or as a decimal. 2:5 in decimals is 0.4.
A rate is a little bit different than the ratio, it is a special ratio. It is a comparison of measurements that have different units, like cents and grams.
A unit rate is a rate with a denominator of 1.
A proportion is an equation that says that two or more ratios are equal.
For example, if one package of cookies contain 20 cookies that would mean that 2 packages contain 40 cookies
A proportion is read as “x is to y as a is to b”.