The Rule of Three Calculator uses the Mathematical Rule of Three, a method of having three numbers to help calculate the unknown, to solve proportions.

## Calculate proportional number

**What is the Rule of Three?**

**The Rule of Three** is a Mathematical Rule that allows you to solve problems based on proportions. By having three numbers: a, b, c, such that, ( a / b = c / x), (i.e., a: b :: c: x ) you can calculate the unknown number. The **Rule of Three Calculator** uses the Rule of Three method to calculate the unknown value immediately based on the proportion between two numbers and the third number.

The working of the **Rule of Three Calculator** can be expressed as follows:

Here, there are two values: A and B and a value of X. In order to find out the value of Y, the Rule of Three tells me that B is related to A and that Y is related to X.

## How does the Rule of Three Calculator work?

Simply fill in the fields of the** Maths Calculator** with the values you want to work out (Value A, Value B and Value X), press the *calculate* button and the **Rule of Three Calculator** will immediately display the missing value of Y.

## An example of the Rule of Three:

An example that you would use to explain the rule of three is as follows:

*If I have 8 litres of paint for 2 bedrooms, how many litres of paint would I need for 5 bedrooms?*

In this case, the two values of A and B are known, A) 2 bedrooms and B) 8 litres. The value of X is also known ( 5 bedrooms) and the missing value is that of Y ( the number of litres) So: