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# 12.2: Multiplication and Division Phrases as Expressions

Difficulty Level: At Grade Created by: CK-12
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Practice Multiplication and Division Phrases as Expressions
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Mrs. Hawk's class hasn't been able to decide which trip to take yet. But they are leaning towards the amusement park.

The amusement park has an cost of 6.50 per student for admission. A couple of students aren't sure that they will be able to go on the trip. The exact number of students attending the trip is unknown. Do you have enough information to write an expression to describe this situation? This is a tricky question that will be answered in this Concept. ### Guidance In the last Concept, you worked on writing addition and subtraction phrases as variable expressions. In this Concept, you will write multiplication and division phrases and single-variable expressions. Let’s start by looking at some of the key words that mean multiplication and division. Multiplication Product, times, groups Division Split up, quotient, divided When deciphering phrases, you will be looking for the same things as the last Concept. 1. Identify any numbers 2. Identify the operation involved 3. Identify the variable The product of eight and a number First, identify any numbers. The number in this phrase is eight. 8 Next, identify the operation. The word “product” means multiply. ×\begin{align*}\times\end{align*} Finally, identify the variable. “A number” means use a variable. y\begin{align*}y\end{align*} Next, we write the expression. 8y\begin{align*}8y\end{align*} Remember that a number next to a variable means multiply. We could also have used parentheses to show multiplication. Now let’s look at a phrase with division. Twenty-four divided by a number First, identify any numbers. 24 Divided ÷\begin{align*}\div\end{align*} A number means use a variable y\begin{align*}y\end{align*} Now put it all together to write an expression 24÷y We could also use a fraction bar to show division. 24y Practice writing expressions from the following phrases. #### Example A Six times an unknown number Solution: 6x\begin{align*}6x\end{align*} #### Example B An unknown number divided by two Solution: x2\begin{align*}\frac{x}{2}\end{align*} #### Example C The product of seven and a number Solution: 7y\begin{align*}7y\end{align*} Here is the original problem once again. Mrs. Hawk's class hasn't been able to decide which trip to take yet. But they are leaning towards the amusement park. The amusement park has an cost of6.50 per student for admission.

A couple of students aren't sure that they will be able to go on the trip.

The exact number of students attending the trip is unknown.

Do you have enough information to write an expression to describe this situation?

We do have enough information to solve this problem, but we can't solve it for the total cost until we know how many students are going on the trip.

The number of students is the variable. We can call that y\begin{align*}y\end{align*}.

We multiply the number of students times the cost.

6.50y\begin{align*}6.50y\end{align*}

### Vocabulary

Here are the vocabulary words in this Concept.

Expression
a variable expression has variables or unknown quantities, numbers and operations without an equal sign.
Variable
a letter used to represent an unknown quantity in an expression or equation

### Guided Practice

Here is one for you to try on your own.

Write an expression for the quantity six times an unknown number divided by 2.

This is tricky because there are two operations in this problem. Let's break it down.

The quantity six times an unknown number becomes 6x\begin{align*}6x\end{align*}.

Divided by two is the next part. We can use a fraction bar for division.

2\begin{align*}\frac{}{2}\end{align*}

Because it is divided by the quantity, we put the 6x\begin{align*}6x\end{align*} on top of the fraction bar.

6x2\begin{align*}\frac{6x}{2}\end{align*}

### Video Review

Here are videos for review.

### Practice

Directions: Write multiplication and division phrases as single-variable expressions.

1. The product of six and a number

2. A number divided by two

3. Fifteen divided by an unknown number

4. A number times seven

5. The product of ten and a number

6. Eighteen divided by a number

7. Twenty times a number

8. A number divided by three

9. An unknown number divided by twelve

10. An unknown number times sixteen

11. The product of five and an unknown quantity

12. The quantity six times an unknown number divided by three

13. The quantity four times an unknown number divided by seven

14. The quantity six times an unknown number divided by ten

15. The product of three and an unknown times four

### Vocabulary Language: English

Variable

Variable

A variable is a symbol used to represent an unknown or changing quantity. The most common variables are a, b, x, y, m, and n.
Variable Expression

Variable Expression

A variable expression is a mathematical phrase that contains at least one variable or unknown quantity.

Oct 29, 2012

Sep 24, 2015