pre-algebra 1-1 variables and expressions 1-1 variables and expressions pre-algebra homework pp. 6-7...
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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
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