Build Your Own Scale Using Equations

Lesson Plan - Get It!

Audio:

Although this is an algebra lesson, you will build your own balance scale and use it to learn about equations!

Before you begin the building process, you will need to understand the vocabulary used in learning this new skill. The words you need to be familiar with are:

• equation
• expression
• balance
• equal
• true
• false

You can use an online dictionary like A Maths Dictionary for Kids to become familiar with the definitions of these terms.

Now, set up an activity where you will read the card and match it with its partner.

Here are the general steps:

1. For this activity, you will use an old deck of playing cards.

2. Cover the front of the cards (the faces) with something you can write on. You can use solid color contact paper or glue or tape white paper to the face of each card.

3. On one card, write a vocabulary word.

4. On another card, write the definition.

5. On the back of those two cards, write a number.

6. Each set of cards (vocabulary and definition) should have the same number on the back of each of them. This way, at the end of the game, you can turn the cards over and see if you matched the vocabulary words and their definitions correctly.

7. Below is a pictorial example. (A larger version of this Match It Example can be found in Downloadable Resources in the right-hand sidebar.)

You can make this set using whatever vocabulary words you need to learn, in any subject. Also, you can expand it to include more words and definitions.

For this activity, you will want to write the vocabulary words stated above and their definitions.

You are now ready to play!

1. Place the cards face up on the table.

2. Your job is to look at the cards and match the card with the vocabulary word with the card that has its definition.

3. Once you have put all of the cards in pairs you can turn them over.

4. The trick is to get the vocabulary word card and the definition card with the same number on the back paired together.

5. If you did not do so well, have your teacher mix up the cards and try again until you pair them up correctly.

Once you have a good understanding of the vocabulary words used in this algebra lesson, it is time to learn how to use equations.

Watch the following KHAN Academy How to test solutions to equations using substitution | 6th grade video to get an idea of what you will be learning today:

Remember, equations use equal signs (=), expressions do not.

You can look at an equation or work out an equation and tell if it is true or false. It is considered true if the answer makes sense and false if it does not.

Look at the examples below:

• 3 + 2 = 5
• 12 - 3 = 10

These examples are pretty easy to figure out. You know that if you add 3 and 2 you will get 5, so that equation is true. However, if you subtract 3 from 12, you do not get 10, so that equation is false.

• Are the following equations true or false given the value of the variable provided for each?

Take a look at how to solve these equations and determine if each one is true given the value of the variable for each:

• 5y = 40    y = 8
• r + 20 = 35    r = 10

Take a moment to figure out each problem and then state whether each equation is true or false.

Just like expressions, equations have variables. The variables are our “unknowns.” You need to figure out what number the variable is representing.

Similar to the expression problems that you worked on, you will substitute a number for the variable in these two problems and see if the answer is correct or makes sense. If so, then it is true. If not, it is false.

Follow along with the examples below:

Step 1: write the original equation

• 5y = 40     y = 8

Step 2: substitute the number 8 for the variable in the equation

• (5)(8) = 40

Step 3: multiply 5 and 8

• 40 = 40

The goal of working with an equation is to balance it. Each side of the equation should end up with the same answer.

In the previous example, each side of the equal sign is 40, so this equation is true.

How about this example:

Step 1: r + 20 = 35     r = 10

Step 2: 10 + 20 = 35

Step 3: 30 = 35

This equation is false. After performing the steps of substituting the number 10 for the variable r and adding 10 and 20, your answer is 30. The other side of the equal sign says 35.

The answers are not balanced; therefore this equation is false.

Continue on to the Got It? section for some practice!