Hey guys! Welcome back to my tutorials on how to solve algebra problems. Let's start by reviewing what we did last time...
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Step 1: Review
In the last instructable, we learned about the Order of Operations or PEMDAS. PEMDAS stands for Parenthesis, Exponents, Multiplication, Division, Addition, and Subtraction. We learned how to deal with parenthesis, using both ways, what exponents look like, and that multiplication & division, and addition & subtraction can be done in the same steps. Make sure you follow this order, because you can end up with greatly differing answers.
Step 2: Intro
This time around, I'll be elaborating upon a subject that y'all may have had questions about in the last instructable (bear with me, How to Solve an Algebra Problem was my first instructable). This subject happens to be variables. .
Step 3: What Is a Variable?
As you may already know from science class, a variable is something that changes. In algebra, the word "variable" has a slightly different definition. A variable in algebra is a letter that represents any possible number. The number that a variable represents changes with every problem.
Step 4: Most Common Variables
Some of the most common variables in algebra are x and y. These are used ALL THE TIME, so it's best to get familiar with them. Like I said last time, we use x so much in algebra that you'll want to stop using x in this form: 10x20= 200. It'll just confuse you. Variables aren't limited to x and y. Any letter in the alphabet will do the job.
Step 5: "Let. . ."
When solving and creating algebra problems, it's always good to be organized. The term "let" will tell you what a variable stands for. For example, "Let n=number of tickets, and C= total cost" Using this information, you can solve a simple algebra problem such as 3.50n=C. So in English, 3.50*the number of tickets= the total cost.
Step 6: Defining Variables Practice
Here's a practice problem: What is the total cost of buying some pants at $15.00 a piece? Define the variables & form an equation.
Step 7: Practice: Naming the Variables
Let's break this problem down. We don't know what the total cost is. This makes 1 variable. We also don't know how many pants we are buying. This makes another variable. The only thing that we DO know is that 1 pair of pants costs $15. Pick a letter for each variable & say what each letter means using "Let."
Step 8: Practice: Forming the Equation
The next thing we have to do is form the equation. In algebra, an equation almost always uses an equals sign, apart from inequalities, which I'll get to in a later instructable. See if you can make an equation yourself. Just remember to have 1 variable on each side of the =.
Step 9: Practice Question Answer
I said that t = total cost, and p = #of pants being bought. Remember from last time that whenever you see a number right next to a variable or a number in a parenthesis, you multiply. Anyway, you multiply the number of pairs of pants being bought by the cost of a single pair of pants to get your total cost. Using this equation, if you are asked "How much money would you spend buying 6 pairs of pants?", you can say that 6*15= your total cost. The picture above/below is my answer.
Step 10: Thanks!
Well, that's it for this instructable! I hope this clarified the basic use of variables for you. If you have a question or would like me to clarify something further, just let me know using the comment box below. Thanks for viewing!