The proportion involving two or more quantities is called Compound proportionality. The quantities could be directly related or inversely related or both.
Rules for Solving Compound Proportions:
- Identify the magnitudes.
- Order the magnitudes and their data, placing the unknown at the end.
- Check if is direct or inverse proportionality. (Identify the proportionality relationship between the magnitude to the unknown datum and the others).
- Transform the data into a proportional fractions. In inverse proportions, operate with inverse fractions.
- Calculate the value of x.
There are two
methods to calculate compound proportionality
problems: the
unitary method or compound
rule of three.
rule of three.
- Rule of three. NOTE: It is useful to write the magnitude with the x datum in the last position.
- The unitary method.
Rule of three:
Ejemplo 1. Si diez
grifos tardan
12 horas en llenar
un depósito de
15 metros cúbicos. ¿Cuánto
tardarán ocho
grifos en llenar un depósito de 7 metros cúbicos?
grifos en llenar un depósito de 7 metros cúbicos?
Magnitudes que interviene:
|
 |
|
El tiempo de llenado es DP a la capacidad. El tiempo de llenado es IP al número de grifos. |
