Pre-Algebra

1-1 Variables and Expressions1-1 Variables and Expressions

Pre-Algebra

HomeworkHomework

pp. 6-7 21 – 60 mult of 3 pp. 6-7 21 – 60 mult of 3

Pre-Algebra

1-1 Variables and Expressions

Warm UpEvaluate.

1. 21 2(3)

5. 9(2.9) [5² - 3(4)]

4. 6(1.4) + (12 - 2²)

3. 2(9) + [2(3) – 2(2)]

2. 4 + 3 9 – 4(4)

Pre-Algebra

1-1 Variables and Expressions

Problem of the Day

Miss Smith obtained the prices below from the landscape company. She plans to buy five birch, two elm, one dogwood, and two oak trees. The landscape company will charge her $15 to plant each tree. How much will it cost?

Trees TreesPrice Price

Maple

Elm

Oak

DogwoodCrab apple

Birch

$16.99

$22.99

$19.99

$23.99

$26.99

$17.99

$337.90

Pre-Algebra

1-1 Variables and Expressions

Review homework from last night

Pre-Algebra

1-1 Variables and Expressions

Obj. - To evaluate algebraic expressions.

Pre-Algebra

1-1 Variables and Expressions

A variable is a letter that represents a value that can change or vary.

The coefficient is the number multiplied by the variable.

Coefficient Variable

The constant is the number that does not change.

+ 7

constant

Pre-Algebra

1-1 Variables and Expressions

To evaluate an algebraic expression, substitute a given number for the variable, and find the value of the resulting numerical expression.

An algebraic expression has one or more variables.

Pre-Algebra

1-1 Variables and Expressions

Evaluate each expression for the given value of the variable.

Example 1:

Substitute 12 for x.

Subtract.

A. x – 5 for x = 12

12 – 5

7

Substitute 4 for y.

Multiply.

B. 2y + 1 for y = 4

2(4) + 1

8 + 1

Add.9

Pre-Algebra

1-1 Variables and Expressions

Evaluate the expression for the given values of the variable.

Example 1C:

C. 6(n + 2) – 4 for n = 5, 6, 7

5

6

7

n Substitute Parentheses Multiply Subtract

6(5 + 2) – 4 6(7) – 4 42 – 4 38

6(6 + 2) – 4 6(8) – 4 48 – 4 44

6(7 + 2) – 4 6(9) – 4 54 – 4 50

Pre-Algebra

1-1 Variables and Expressions

Evaluate each expression for the given value of the variables.

Example 2:

Substitute 2 for x and 1 for y.

Multiply.

A. 4x + 3y for x = 2 and y = 1

4(2) + 3(1)

8 + 3

Substitute 2 for r and 5.5 for p.

Multiply.

B. 8.5 r – 2p for r = 2 and p = 5.5

8.5(2) – 2(5.5)

17 – 11

Add.11

Subtract.6

Pre-Algebra

1-1 Variables and Expressions

Evaluate each expression for the given value of the variables.

Try This:

Substitute 3 for x and 4 for y.

Multiply.

C. 3x + 2y for x = 3 and y = 4

3(3) + 2(4)

9 + 8

Substitute 2.5 for q and 2 for r.

Multiply.

D. 8q – 3.5r for q = 2.5 and r = 2

8(2.5) – 3.5(2)

20 – 7

Add.17

Subtract.13

Pre-Algebra

1-1 Variables and Expressions

Use the expression 1.8c + 32 to convert the boiling point temperature from degrees Celsius to degrees Fahrenheit.

Example 3:

Substitute 100 for c.

Multiply.

A. Boiling point of water at sea level: 100°C

1.8(100) + 32

180 + 32

1.8c + 32

Add.212

100°C = 212°F

Water boils at 212°F.

Pre-Algebra

1-1 Variables and Expressions

Lesson Quiz

Evaluate each expression for the given values of the variables.

1. 6x + 9 for x = 3

2. x + 14 for x = 8

3. 4x + 3y for x = 2, y = 3

4. 1.6x – 2.9y for x = 19, y = 6

5. If n is the amount of money in a savings account, then the expression n + 0.03n can be used to find the amount in the account after it has earned interest for one year. Find the total in the account after one year if $500 is the initial amount.

27

22

17

13

$515