Ratio
For example, if a school has 20 teachers and 500 pupils, then the ratio of teachers to students is written as 20:500 (and pronounced as "20 to 500"). As another example, if a cake mix asks for 100 grams of flour, 300 grams of butter and 25 grams of sugar, then the ratio of flour to butter to sugar is written as 100:300:25 (and pronounced as "100 to 300 to 25").