Jae is creating a model building for a design competition. Each floor will be
inches tall. How can Jae find the total height of his building model. How tall will it be if Jae decides to have 10 floors?In this concept, you will learn how to evaluate expressions and products of fractions.
Evaluating Expressions with Products of Fractions
An expression is a numerical phrase that combines numbers and operations but no equal sign.
There are two kinds of expressions. Numerical expressions include numbers and operations only. Algebraic expressions include numbers, operations, and variables.
Types of Expressions
Includes  Examples  

numerical expressions  numbers, operations 

algebraic expressions  numbers, operations, variables 

Since a numerical expression includes numbers and operations, perform the operation required to evaluate. To evaluate means to find the value of the expression.
Evaluate the numerical expression.
Notice that there are two sets of parentheses. Remember that the parentheses can identify groups and also indicate multiplication.
Evaluate by multiplying and then simplifying or by simplifying first then multiplying.
The answer is in simplest form.
The value of the expression is
As you learn about algebra and higher levels of math, you will be working with algebraic expressions.
An algebraic expression is similar to a numeric expressions, except that it uses variables. Variables are letters that represent an unknown number. Sometimes the values of the variables are given.
Evaluate the algebraic expression.
To evaluate this expression, substitute the given values for
Then, simplify the expression. Cross simplify the 3s with the greatest common factor (GCF) of 3. Each three becomes a one.
Next, multiply to evaluate the expression.
The value of the expression is
Examples
Example 1
Earlier, you were given a problem about Jae and his design competition.
Jae is making a model building where each floor is
For Jae's model building, he can create an algebraic expression to determine the height of his model. The total height will be the the height of each floor times the number of floors.
Find the height of the model when x = 10.
First, substitute the variable with the given value.
Then, convert the mixed number and whole number into an improper fraction.
Next, simplify the fractions.
Finally, multiply the fractions.
Jae's 10 floor model will be 35 inches tall.
Example 2
Evaluate
First, substitute the values into the expression.
Then, simplify the expression.
Next, multiply the fractions.
The answer is
Example 3
Evaluate
First, simplify the fractions.
Then, multiply.
The value of the expression is
Example 4
Evaluate
First, substitute the values into the expression.
Then, simplify the fractions.
Next, multiply.
The value of the expression is
Example 5
Evaluate
First, simplify the fractions.
Next, multiply.
The value of the expression is
Review
Evaluate each expression. Answer in simplest form.
 Evaluate
(xy) whenx=23 andy=610  Evaluate
(xy) whenx=13 andy=410  Evaluate
(xy) whenx=1213 andy=26  Evaluate
(xy) whenx=13 andy=45  Evaluate
(xy) whenx=79 andy=321  Evaluate
(xy) whenx=45 andy=1620  Evaluate
(46)(12)  Evaluate
(19)(618)  Evaluate
(49)(14)  Evaluate
(411)(1112)  Evaluate
(910)(56)  Evaluate
(89)(36)  Evaluate
(1819)(36)  Evaluate
(49)(3640)  Evaluate
(1214)(78)
Review (Answers)
To see the Review answers, open this PDF file and look for section 7.5.