Write ExpressionsWrite ExpressionsSection 1.3Section 1.3

#3 Only having one truth about each object, whoever finds it

knows as much as one can know about it. Rene Descartes

The ConceptThe Concept• Yesterday we discussed the Order of

Operations and it’s place in the basic skill set of Algebra

• Today we’re going to work with our ability to translate phrases into mathematical statements

• This skill will aid us in our ability to handle higher level problems as well as word problems

Arithmetic OperatorsArithmetic OperatorsFor our purposes we have five basic arithmetic operations

The book only lists 4, but it’s important for us to include powers.

They are

• Addition• Subtraction• Multiplication• Division• Powers

Key WordsKey WordsFor each of our operators, there are specific words that

indicate their use

These can be found on page 15

We use these key words along with our understanding of numbers and variables to translate phrases into expressions

Expressions are mathematical statements that lack an equality or inequality sign

ExamplesExamples• 4 less than the quantity 6 times a number n

6 4n

222 m

3( 4)t

3 7a

• The difference of 22 and the square of a number m

• The product of a number 3 and 4 less than a number t

• The sum of 3 times a number a and 7

ExamplesExamples• 4 less than the quantity 6 times a number n

6 4n

222 m

3( 4)t

3 7a

• The difference of 22 and the square of a number m

• The product of a number 3 and 4 less than a number t

• The sum of 3 times a number a and 7

Practical situationsPractical situationsSimilarly, we can use these words in conjunction with an

understanding of real world situations to write what the book calls verbal models.

For instance, what expression would we write given this statement?

• The number of pencils in Ms. Jacksons office if each box contains 12 pencils and she has n boxes.

• The number of pieces of pizza each person out of a group of 7 gets if they order p pizza and each one has 8 slices.

Practical situationsPractical situationsWhile it may seem that verbal models are somewhat of a step

back, they do aid in the processing of word problems.

For instance• The new Honda Insight gets 41 miles per gallon. Write an

expression that models the total number of miles driven on g number of gallons of gas and then evaluate the expression for 11 gallons.

Unit RatesUnit RatesAnother item that this section focuses on is the concept of a

unit rate.

A unit rate is the rate of consumption of an item.

For instance

The unit rate for the number of classes in a school day is 8 classes per day

ExampleExampleYour printer takes 36 seconds to print a small photo and 60 seconds to print a large one. Write an expression

for the time (in seconds) your printer would take to print a batch including both small and large photos. Then find the time your printer would take to print 12 small photos and 5 large photos.

Most Important PointsMost Important Points• Key Words

HomeworkHomework

• 1.2

p18 1, 2-32 even, no 30