# What are Proportions?

A proportion is a statement that equates two ratios. For example, suppose that baking a single cake requires 250 g of chocolate. Then you know that 500 g of chocolate are needed to bake two cakes. This can be expressed as a proportion equation:

250 g chocolate /1 cake  = 500 g chocolate/2 cakes

This is read as "250 g of chocolate is to 1 cake as 500 g of chocolate is to 2 cakes ".

A proportion statement is an equation because there is an = sign.

Many situations in the laboratory require the same reasoning as the above example.  For example, if 10 g of glucose are required to make 1 L of a nutrient solution, how many grams of glucose are needed to make 3 L of nutrient solution? 30 g of glucose would be required.