### Compound rule of three

Compound rule of three is a set of two or more simple rule of three. The simple rule
of three is a method to solve proportions. If you have three numbers: a, b, c, such that, a / b = c / x, you can
calculate the unknown value (x).

To solve the Rule of three compound is necessary to check whether each quantity is a direct proportion, or inverse, to the unknown value of (x).
For inverse proportion changes the numerator by denominator and vice versa.

**Direct Proportion**

If a change in a quantity causes a change in another quantity of the same proportion, the amounts are in direct proportion.

**Inverse Proportion**

When, the increase of an element, causes a decrease in the other one, or by the contrary, a decreasing causing the increase in the other one, this is, an
inverse proportion.

See full text: Compound Rule of three

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