# Lesson Tutor : Lesson Plans : Algebra Grade 9 Translating word sentences to math equations.

Basic Algebra – Lesson 2
by Elaine Ernst Schneider

Objective(s): By the end of this lesson the student will be able to: translate a word sentence into a mathematical expression.

Pre-Class Assignment:  Completion of Basic Algebra – Lesson 1

Resources/Equipment/Time Required:

Outline:

In the first lesson, you learned that numbers and variables form sentences, or algebraic “expressions.” When you take information from a sentence and turn it into a mathematical expression, it is called “translating.”

A place to begin:

1. When you write algebraic expressions, use +, -, and = signs. For division, use / , the same way you know that when you see a fraction, it means to divide the top number by the bottom number.
2. For multiplication, write the expression with no symbol or sign between them as the X (multiplication) symbol can be confused with the variable x. For example 3 times the variable y should be written 3y. You can also use parentheses to indicate multiplication. This is especially useful in longer problems such as (3y)(4-2x).
3. When you want to multiply something AFTER another expression has been done first, use parenthesis. For example, if you want to add x and y and THEN multiply the result by 7, write it this way: 7(x + y).
4. To translate from language to a math expression, read the sentence carefully. Then decide what operations it will take to reach a solution. Write this into an algebraic expression.

Let’s Get Started:

Here is the word problem:

I am stocking shelves at a T-shirt store. I have been given eight boxes of T-shirts. There are 25 T-shirts in each box. My instructions are to take one T-shirt from every box and set it aside to be given to the poor. How many T-shirts will be left for me to put on the store shelves after I sort out the T-shirts to be given to the poor?

Here is the algebraic expression:

8(25-1)

8(24)

192

If you don’t know the number of T-shirts in each box, then substitute the variable x for that. Then the expression would look like this:

8(x – 1)

Now it’s time for you to try a few.

Assignment(s) including Answer key:

EXERCISE:

1. Katie is 21 years old. Write an algebraic expression that tells how old she will be in five years. Let x represent that age. Solve from your expression.
2. One hamburger costs x cents. Write an algebraic expression that tells how much 4 hamburgers will cost.
3. Sandy is 21 years old. Al is five years older. How old will Al be in five years? Let x represent Al’s age in five years. Solve for x.
4. I have ten hats that cost \$47.50 for all of them. Write an algebraic expression to show how much one of those hats cost, letting y represent the answer. Solve for y.
5. I have ten hats that cost \$47.50 for all of them. How much will I have to sell EACH hat for to make a profit of \$1 on each? Set it up in an algebraic expression to solve.

ANSWER KEY Click Here:

Pre-Requisite To:   Basic Algebra – Lesson 3 Solving for X

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