Weight Loss Made a Bit Easier: Realistic and Practical Advice for Healthy Eating and Exercise
Available on Amazon.com in paperback/Kindle formats for $6.25/$2.99. Please click here for details.
Home | My Math and Education Books | Math Lessons | Ask a Math Question
Site Info | Contact Info | Tutoring Info | LarryZafran.com | Tweet
Lesson 76: Introduction to Solving Equations with Variables
We've mentioned variables in an earlier lesson. This lesson introduces you to the very basics of solving equations with variables, and this will start you on the road to the study of algebra which is huge component of math.
In math, a variable is a letter that we use to represent an unknown quantity. Very often we use x, but we can use any letter at all. Note that now that we'll start using x to represent unknown quantities, we can no longer use it to represent multiplication. We have to use the middle dot like we've seen before, or no symbol at all, such as using 7x to represent 7 times x.
Let's look at some basic equations with variables:
9 + x = 17. What does x equal? We can just use our basic math knowledge to see that it equals 8. We could also just do 17 - 9 to figure out the answer. Later you'll learn methods of solving problems like this if the problem is more complicated.
8x = 56. x = 7. We can count by 8s to see that we need 7 of them, or we can do 56 ÷ 8 to get 7.
We can also use variables as part of solving word problems. For example, let's say a word problem says that Billy has 5 more apples than John does. We can use B to represent Billy's apples, and we can write B = J + 5, to show that Billy has the amount that John has, plus 5 more, using J to represent the number of John's apples. Once we know the value of J, we could then find the value of B.
Another example that comes up a lot is that someone has fewer objects than another. If Steve has 7 fewer apples than Mary does, we can use the equation S = M - 7 to represent the number of Steve's apples.
Later you will have much, much more practice using variables in equations.
Remember that you can ask a math question if you have additional questions about a topic, or you can contact me if you have any comments or suggestions for this site.