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Grade: Senior
Subject: Mathematics

#3703. Variables

Mathematics, level: Senior
Posted Sat Dec 30 13:42:55 PST 2006 by Guido Feliz, Jr (
DOE, New York, NY
Materials Required: Pencil, Math notebook
Activity Time: Flexible
Concepts Taught: Learning the Importance of Variables

Topic: Variables

What is a variable?

Students solve algebra problems everyday not knowing the meaning of the word variable.

A variable is quantity we do not know the value of. The word variable means having the ability to change. In math, we use letters of the alphabet to represent variables.

The most popular variables in algebra are x and y. However, ANY letter can be used as a variable.

For example, in x + 5, x is the missing information we need to find. The number 5 is called the CONSTANT because, unlike x, the number 5 remains the same.

When selecting different values for x, the sum will be different. Let's see what happens.

Sample A:

What is x + 5 when x = 10?

I replace x with 10 and then add 10 to 5. What is my answer? My answer is 15.

Sample B:

When x = 4, what is x + 5?

I simply replace x with 4 and then add 4 to 5. What is the new sum? The answer is 9.

Notice that I simply replaced x with 10 and 4 in two different examples but 5 did not change its value. See it?

This clearly shows that x CHANGED in value but 5 did NOT change its value.

By Guido Feliz, Jr