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WARM -UP
Add or subtract Multiply or divide1. -12+(-5) 5. -13*52. 9-(-4) 6. 3. 5+(-7) 7. 4.2*0.34. -8+(10) 8.
Warm –up answers
Add or subtract Multiply or divide1. -12+(-5) -17 5. -13*5 -652. 9-(-4) 13 6. -503. 5+(-7) -2 7. 4.2*0.3 1.264. -8+(10) 2 8. 660
Variables and expressions
• Objectives: • Translate between words and algebraic
expressions• Evaluate algebraic expressions
Variables and expressionsvocabulary
• variable: is a letter or symbol used to represent a value that can change.
• Constant: is a value that does not change.• Numerical expression: may contain only
constants and/or operations.• Algebraic expression: may contain variables,
constants and/or operations.
Variables and expressionsvocabulary examples
• Give examples for the following:• Variables :
• Constants:
• Algebraic Expressions:
Variables and expressionsDiagram
+ Plus, sum , increased by , more than
__ Minus, difference, less than
* Times, product ,equal group of, multiply by
Divided by, quotient
Use diagram to help translate algebraic expressions to words
Variables and Expressions Translate from algebraic expression to words
I. Give different ways to write each algebraic expression into words Example 1: A) x+5 • The sum of x and 5• Five more than x• X plus 5• X increased by 5
Translate from algebraic expressions to words
B) m-6• The difference of m and 6• 6 less than m• m minus 6
C) 3*k• The product of 3 and k• 3 times k
Translate from algebraic expressions to words
• Student practice :• Check it out 1a to 1d1a. 4-n 1c. 9+q
1b. 1d. 3(h)
Variables and expressions Diagram
• Use to help you translate words into algebraic expressions
Add Put together, combine
Subtract Find how much more or less
Multiply Put together equal groups
divide Separate into equal group
Translate words into algebraic expressions
• Example 2:A) Evelyn has 2 more years than her sister
Adriana. Write and expression for Evelyn’s age.
* a+2B) Sam is 3 years younger than sue, who is y years old. Write an expession for sam’s age.* y-3
Translate words into algebraic expressions
• Words to look for that will help you with translation
addition sum , more
Subtraction Less, difference, minus
Multiplication Per, times, product
Division Quotient, ratio
Translating words into algebraic expressions
C) Mario’s car is going 55 miles per hour. Write an expressions for how fast is Mario’s car going. • 55 hD) William runs a mile in 15 minutes. Write a an
expression for the number of miles that william run in m minutes.
* • Student Practice : check it out 2a-2c
Evaluating Algebraic Expressions
• Evaluate: is to find its value. • Substitute: to replace • To evaluate an algebraic expression substitute
the variables in the expression for numbers and then simplify as needed.
• Hint: Usually they give the numbers you need to substitute the variables for.
Evaluating Algebraic Expressions
• Example 3: Evaluate each expression for x=8 , y=2 and z=4
A) x+z x+z= 8+4 * substitute x with 8 and z with 4 = 8+4= 12 simplify
Evaluating Algebraic Expressions
B) xyzxyz = 8*2*4 substitute x,y and z with 8,2 and 4 = 8*(2*4)=8*8 simplify = 64
= substitute== 4 simplify
Student Practice
• Evaluate the following expressions give x=3,y=-7 and z=5
• A) xy B) 2x+y C) x-z-y* Check it out 3a-5
Evaluating Algebraic Expressions
• Example 4: Challenge• Example 5:Comparing cellphones plans*Lets says company AC has a plan that consists of $35 plan fee for the first 600 minutes plus 10 cents per minute pass the 600 minutes.• Company BC has a plan that consists of $25 plan fee
for the first 600 minutes plus 25 cents per minute pass the 600 minutes.
• which plan is less expensive for 800 minutes?