Math 6H (Period 3)

Writing Expressions 5.1

To use algebra in solving real-life problems, you need to translate words, phrases and sentences into mathematical symbols. Fist look for the words that indicate operations.

We went through several examples for each operation:

Translating Addition Phrases:

Ten more than a number     à x + 10

The sum of -8 and a number à -8 + y

A number plus 3 à n + 3

Translating Subtraction Phrases

Five minus a number à 5 - x

The difference of 3 and a number à  3 – n

Nine less than a number à  y – 9

Translating Multiplication Phrases

Five times a number à  5y

The product of 7 and a number à  7x

A number multiplied by -2 à -2m

Translating Division Phrases

The quotient of a number and 6 à x/6

Five divided by a number à  5/n

REMEMBER: Subtraction and division are NOT commutative. the order in which you write the numbers and variables changes the meaning of the variable expression.  

We then discussed the problem in our textbook on page 218

You join a health club that has a membership fee and a tennis court fee. According to the sign in the textbook, the membership is $25 a month and the court fee is $5 per use. We had to write an expression for your total  monthly cost.

MEMBERSHIP FEE   + COURT FEE · NUMBER OF TIMES YOU USED THE COURT

Let n = the number of times you use a court.

25 + 5n

We went through Problems # 24-27 on Page 219

A truck traveled 65 miles per hour for a number of hours, To find the number of miles traveled... youà multiply. The distance traveled equals the product of the rate of travel and the time traveled.

Your regular paycheck is increased by $65 for working overtime. To find the total amount of your paycheck... youà add; “increased by” indicated addition.

Sixty-five fewer people came than the number expected. To find the number of people who came ...you à subtract; “fewer” indicates subtraction

Your grandmother is 5 years younger than her brother. To find your grandmother’s age ...youà subtract; “younger than” indicates subtraction.