OML Search

Cross Multiply




 
Related Topics:
More Lessons for Algebra

Math Worksheets

Simplifying equations is often the first step to solving algebra equations with fractions. There are more techniques to simplify equations, for eg. Combine Like Terms, Multiplication and Division of Terms, Removal of Brackets - Distributive Property

In this lesson, we will learn cross multiplication.

Cross Multiplication

Cross multiplication allows you to remove denominators from fractions in an equation. Note that this technique applies only towards simplifying equations, not to simplifying expressions.

For example, if you have the equation:

2/3=a/6

then you can multiply the numerator of one fraction with the denominator of the other fraction (across the = sign) as shown:

2/3=a/6

to obtain the equation

(2 × 6) = a × 3

Example::

Simplify: 4/5=8/a

Solution:

Step 1: Cross Multiply

4 × a = 8 × 5
4a = 40

Step 2: Isolate variable a

a=40/4=10

Answer: a = 10




How to Cross Multiply Proportions?

Cross multiplying proportions is a straightforward process that is the same as cross multiplying fractions. Cross multiply by multiplying a numerator by the other side's denominator. The following video shows some examples of cross multiplication.

Solving Proportions with Mixed Numbers
In order to make solving proportions with mixed numbers easier, we simply turn the mixed number into an improper fraction. We then solve the proportions with mixed numbers by using cross multiplication.


 

You can use the Mathway widget below to practice Algebra or other math topics. Try the given examples, or type in your own problem. Then click "Answer" to check your answer.


OML Search


We welcome your feedback, comments and questions about this site or page. Please submit your feedback or enquiries via our Feedback page.


[?] Subscribe To This Site

XML RSS
follow us in feedly
Add to My Yahoo!
Add to My MSN
Subscribe with Bloglines