1.1 Variable and Expressions: Quantity: Anything that can be measured or counted. Variable: A symbol, usually a letter, used to represent the value of a variable quantity. Algebraic Expression: A mathematical phrase that includes one or more variables. Numerical Expression: A mathematical phrase involving numbers and operation symbols, but not variables. GOAL: REAL-WORLD: A student writes the word phrase “the quotient of n and 5” to describe the expression 5/n. Describe and correct the student’s error. SOLUTION: Using the definition of quotient = fraction, we see that : 5/n the quotient of 5 and n. n/5 the quotient of n and 5. Thus the student has the two variables backwards. YOU TRY IT: Write an algebraic expression for the following sentence: “8 minus the product of 9 and r” SOLUTION: Using the basics we learned in Pre-Algebra we know that : Minus subtraction Product multiplication 8 minus 8 Product of 9 and r 9r Therefore: 8 – 9r is the expression. YOU TRY IT: Write an algebraic expression for the following sentence: “3 less than 2 times a number” SOLUTION: Using the basics we learned in Pre-Algebra we know that : 3 Less than subtraction placed at the end of the sentence - 3 2 times multiplication 2( ), 2∙, 2× A number n to represent any number Therefore: 2n- 3 is the expression. VIDEOS: Variables and Expressions Variables: http://www.khanacademy.org/math/algebra/intro duction-to-algebra/variable-andexpressions/v/what-is-a-variable Expressions: http://www.khanacademy.org/math/algebra/intro duction-to-algebra/variable-andexpressions/v/variables-and-expressions-1 CLASSWORK: Page 20-22: Problems: 1, 3, 5, 6, 7, 10, 24 33, 37, 46, 56.