Presentation on theme: "Variables and Expressions"— Presentation transcript:
1 Variables and Expressions Chapter 1-1Prentice Hall Pre Algebra8th Grade Math
2 Check Skills You’ll Need How many days in a week?7 days in a weekHow many inches in a foot?12 inches in a footHow many cents is a nickel?a nickel is 5 centsHow many quarts is a gallon?4 quarts is a gallonHow many feet is a yard?3 feet is a yard
3 Definitions NUMERICAL EXPRESSION VARIABLE VARIABLE EXPRESSION a mathematical phrase that uses numerals and operation symbols.VARIABLEIs a letter that stands for a numberVARIABLE EXPRESSIONa mathematical phrase that uses variables, numerals, and operation symbols.
4 ExamplesIdentify each expression as a numerical expression or a variable expression. For a variable expression, name the variable.7 – 5Numerical expressiona + 4Variable expressiona is the variable
5 Quick CheckIdentify each expression as a numerical expression or a variable expression. For a variable expression, name the variable.8 ÷ xVariable expression, x is the variable100 × 6Numerical expression, no variablesd + 43 – 9Variable expression, d is the variable4aVariable expression, a is the variable
6 Real-World Problem Solving ScienceThe fastest dinosaur may have been Ornithomimus, which could run about 60 ft. in a second. Write a variable expression for the distance Ornithomimus could run in a given time.We know that the dino runs 60 ft in one second.We can label the time in seconds with letter s.We multiply 60ft with by seconds s to find out the distance the dino runs in s seconds.60 ∙ s or 60sCan you find out how far the dino runs in one minute?360 ft. in one minute
7 Quick CheckBagels cost $.50 each. Write a variable expression for the cost of b bagels.0.50bWrite a variable expression for the number of hours in m minutes.60h
8 Exercises Write a variable expression for each word phrase: 10 less than pp – 104 fewer than jj - 43 divided by n3 ÷ nThe sum of 18 and c18 + c or c + 18
9 Write an expression The number of days in 4 weeks 7 ∙ 4 or 4 ∙ 7The number of days in w weeks7wNumber of feet in 100 inches100 ÷ 12Number of feet in i inches12i
10 The Order of Operations Chapter 1-2Prentice Hall Pre Algebra8th Grade Math
11 Order of Operation Rule: Parenthesis Exponents Multiplication or DivisionAddition or SubtractionWhen there are two operation with the same rank, you need to solve them from Left to Right.
12 Example Using order of operation 6 + 15 ÷ 3 (divide) 6 + 5 (then add) 11CORRECTNot using the order of operation÷ 3 (add)21 ÷ 3 (then divide)7WRONG
13 Example18 ÷ 3 ∙ 2Same rank operation therefore solve from left to write (division first)6 ∙ 212CORRECT18 ÷ 3 ∙ 2Not using order of operation and doing the multiplication first.18 ÷ 63WRONG
14 Order of Operation Rule: Parenthesis Exponents Multiplication or DivisionAddition or SubtractionWhen there are two operation with the same rank, you need to solve them from Left to Right.
17 ProblemA customer buys orange juice for $.95 and two apples for $.55 each. She gives the cashier a five dollar bill. How much change should the cashier give the customer? (write the numerical expression and than solve the problem)5 − ( × 0.55)$2.95
18 Solving Problems What you need to know to solve this problem: Area of a rectangle is length times widthA = L x WWrite the numerical expression prior to calculations.Find more than one way to solve the problem.Urban PlanningSome urban planners specialize in planning entire new towns. These towns are designed for livability, with plenty of open space. The sketch shows the dimensions for a new town called Panorama. Find Panorama’s area.