Proportions
A proportion is a comparison of two equal ratios , that can also be written as an equation of this form:
This is read is to as is to . In this equation, and are called the means , and and are called the extremes .
These can be solved by taking cross products (also known using the means-extremes property or cross multiplication).
Example 1:
Solve the proportion: .
Take the cross product and solve the resulting equation.
Example 2:
If there are packets of peanuts in boxes, how many boxes will you need to have packets?
First, write a proportion. Note that the numbers of packets are the numerators, and the numbers of boxes are the denominators.
Take the cross product and solve the resulting equation.
Divide both sides by .