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Objectives. Translate between words and algebra. Evaluate algebraic expressions. A variable is a letter or a symbol used to represent a value that can change. A constant is a value that does not change. A numerical expression contains only constants and operations.

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Objectives

Translate between words and algebra.

Evaluate algebraic expressions.


A variable is a letter or a symbol used to represent a value that can change.

A constant is a value that does not change.

A numerical expressioncontains only constants and operations.

An algebraic expression may contain variables, constants, and operations.


You will need to translate between algebraic expressions and words to be successful in math.

Plus, sum,

increased by

Minus, difference, less than

Divided by, quotient

Times, product, equal groups of


Writing Math words to be successful in math.

These expressions all mean “2 times y”:

2y 2(y)

2•y (2)(y)

2 x y (2)y


Example 1: Translating from Algebra to Words words to be successful in math.

Give two ways to write each algebraic expression in words.

A. 9 + r B. q – 3

the difference of q and 3

the sum of 9 and r

9 increased by r

3 less than q

C. 7mD. j  6

the product of m and 7

the quotient of j and 6

m times 7

j divided by 6


Example 2A: Translating from Words to Algebra words to be successful in math.

John types 62 words per minute. Write an expression for the number of words he types in m minutes.

m represents the number of minutes that John types.

Think: m groups of 62 words

62 · m or 62m


Example 2B: Translating from Words to Algebra words to be successful in math.

Roberto is 4 years older than Emily, who is y years old. Write an expression for Roberto’s age

y represents Emily’s age.

y + 4

Think: “older than” means “greater than.”


To words to be successful in math. evaluatean expression is to find its value.

To evaluate an algebraic expression, substitute

numbers for the variables in the expression and

then simplify the expression.


Example 3: Evaluating Algebraic Expressions words to be successful in math.

Evaluate each expression for a = 4, b =7, and

c = 2.

A. b – c

b – c = 7 – 2

Substitute 7 for b and 2 for c.

Simplify.

= 5

B. ac

Substitute 4 for a and 2 for c.

ac = 4 ·2

= 8

Simplify.


Check It Out! words to be successful in math. Example 3

Evaluate each expression for m = 3, n = 2, and

p = 9.

a.mn

mn = 3 · 2

Substitute 3 for m and 2 for n.

= 6

Simplify.

b. p – n

Substitute 9 for p and 2 for n.

p – n = 9 – 2

= 7

Simplify.

c. p ÷ m

p ÷ m = 9 ÷ 3

Substitute 9 for p and 3 for m.

= 3

Simplify.


Example 4A: Recycling Application words to be successful in math.

Approximately eighty-five 20-ounce plastic

bottles must be recycled to produce the fiberfill

for a sleeping bag.

Write an expression for the number of bottles needed to make s sleeping bags.

The expression 85s models the number of

bottles to make s sleeping bags.


Example 4B: Recycling Application Continued words to be successful in math.

Approximately eighty-five 20-ounce plastic

bottles must be recycled to produce the fiberfill

for a sleeping bag.

Find the number of bottles needed to make

20, 50, and 325 sleeping bags.

Evaluate 85s for s = 20, 50, and 325.

To make 20 sleeping bags, 1700 bottles are needed.

85(20) = 1700

To make 50 sleeping bags, 4250 bottles are needed.

85(50) = 4250

To make 325 sleeping bags, 27,625 bottles are needed.

85(325) = 27,625


Do You Know It? words to be successful in math.

Give two ways to write each algebraic

expression in words.

1. j – 3

2. 4p

3. Mark is 5 years older than Juan, who is y years old. Write an expression for Mark’s age.

The difference of j and 3; 3 less than j.

4 times p; The product of 4 and p.

y + 5


d words to be successful in math.

1

e

2

Do You Know It?

Evaluate each expression for c = 6, d = 5, and e = 10.

4. 5.c + d

Shemika practices basketball for 2 hours each

day.

11

6. Write an expression for the number of hours she

practices in d days.

7. Find the number of hours she practices in 5, 12,

and 20 days.

2d

10 hours; 24 hours; 40 hours


Homework
Homework words to be successful in math.

Section 1.1 – Variables and Expressions

pages 9-11

#’s 18 – 46 EVEN


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