Rule of Three
In a situation of proportionality, the mathematical reasoning that makes it possible to determine a missing term when you know all of the other terms.
This proportional reasoning, gave rise to an algorithm called cross multiplication, which is easy to visualize and to apply.
Example
We used 8 litres of paint to repaint the walls of a room with a surface area of 40 m². How many litres of paint would we need to repaint the walls of a room with a surface area of 60 m²? |
This arrangement leads to the equation: 40x = 8 • 60 by multiplying the terms diagonally. Therefore, x = 12. |