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Bell Ringer. In a factory of 200 people, 120 are men who earn $18 an hour. The women earn $20 an hour. What is the average salary of the employees at the factory? Men: 120 • $18 = Women: 80 • $20 = Total: $2160 + $1600 = Average: $3760 ÷ 200 =. $2160. $1600. $3760. $18.80 an hour.
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Bell Ringer • In a factory of 200 people, 120 are men who earn $18 an hour. The women earn $20 an hour. What is the average salary of the employees at the factory? • Men: 120 • $18 = • Women: 80 • $20 = • Total: $2160 + $1600 = • Average: $3760 ÷200 = $2160 $1600 $3760 $18.80 an hour
Variable • A variable is a letter or symbol that represents a number (unknown quantity). • 8 + n = 12
Variable • A variable can use any letter of the alphabet. • n + 5 • x – 7 • w – 25
Algebraic Expression • a group of numbers, symbols, and variables that express an operation or a series of operations. • m + 8 • r – 3 • 3n
Evaluate Expressions • Evaluate an algebraic expression – To find the value of an algebraic expression by substituting numbers for variables. • m+ 8 m = 2 • r – 3 r = 5 2 + 8 = 10 5 – 3 = 2
Simplify • Combine like terms and complete all operations • Simplify: m+ 8 + m • 2 m + 8
The Great Dane • Although they are closely related, a Great Dane weighs about 40 times as much as a Chihuahua. • An expression for the weight of the Great Dane could be 40c, where c is the weight of the Chihuahua. • When solving real-world problems, you will need to translate words, or verbal expressions, into algebraic expressions.
Expressions • In order to translate a word phrase into an algebraic expression, we must first know some key word phrases for the basic operations.
Words That Lead to Addition • Altogether • Greater Than • Add • Total • Sum • More than • Increased • Plus
Words That Lead to Subtraction • Decreased • Less • Difference • Minus • How many more • Take away • Subtract
Words That Lead to Multiplication • Product • Times • Multiply • Of • Twice • Double • Triple
Words That Lead to Division • Quotient • Divide • Divided by • Split equally
Multiplication • Multiplication expressions should be written in side-by-side form, with the number always in front of the variable. • 3a 2t 1.5c 0.4f
Division Division expressions should be written using the fraction bar instead of the traditional division sign.
Addition Phrases 1. 3 more than x x + 3 2. the sum of 10 and a number c 10 + c 3. a number n increased by 4.5 n + 4.5
Subtraction Phrases 1. a number t decreased by 4 t – 4 2. the difference between 10 and a number y 10 – y 3. 6 less than a number z z – 6
Multiplication Phrases 1. the product of 3 and a number t 3t 2. twice the number x 2x 3. 4 times a number e 4e
Division Phrases 1. the quotient of 25 and a number b 25 / b 2. the number y divided by 2 y / 2 3. 5 divided by g 5 / g
Write Algebraic Expressionsfor These Word Phrases n + 10 • Ten more than a number n • A number w decreased by 5 • 6 less than a number x • A number n increased by 8 • The sum of a number n & 9 • 4 more than a number y w - 5 x - 6 n + 8 n + 9 y + 4
Write Algebraic Expressionsfor These Word Phrases s + 2 • A number s plus 2 • A number k decreased by 1 • 31 less than a number x • A number b increased by 7 • The sum of a number n & 6 • 9 more than a number z k - 1 x - 31 b + 7 n + 6 z + 9
Write an Algebraic Expression for These Situations • Scott’s brother is 2 years younger than Scott • The sum of two numbers is 12 • The difference between two numbers is 5 s - 2 v + c = 12 m – n = 5