# How to calculate Proportions

Proportions can be seen in many aspects of life. From mixing the baby formula to knowing how to divide a cake among children, the proportions are very useful to describe the relationship between two quantities.

## Computer ratios

Define the problem To calculate a proportion, the two quantities that are compared must be known. To simplify, let’s call them A and B.

Determine what amount is divided. The amount that is divided usually appears before an”a “or”by “in a problem, and is being divided by the next number. For example, in miles per gallon, the total number of miles is being divided by the number of gallons used.

Express the quantities in numbers. In order to calculate the ratio, the numbers are used and divided to obtain the result.

Make the division. Suppose there are 50 of A and 10 B. Then the proportion is: A / B = 50/10 = 5 A for B.

Use the ratio as necessary. For example, suppose I have 30 B now. Then, according to the ratio of 5 A to B, I have: 30 B 5 times A for B is 30 * 5 = 150 A.

**Tips**

When you have three or more quantities, you can calculate more than one reason. For example, I can have A for B and B for C. The combination of these two gives A for C.