Variables and Expressions

September 21, 2009

Warm upSpiral Review and Test Prep 1-13 Show your work.

1. Evaluate 63. 5. Belinda borrowed $137 from her parents. She is planning to pay her parents $20 a week. How many weeks will it take Belinda to pay for her lessons?

2. Round to the nearest ten million.348,298,726

6. Fill in the blank and tell the property the problem shows.(8 x 6) ___ = 8 x (6 x5)

3. (14-6) x (6-3)+14/2= 7. Mia biked the 9-mile trail and then the 15-mile trail. Josef biked the 15-mile trail and then the 9-mile trail. Using one of the properties, write a number sentence to show that each traveled the same distance.

4. Divide.234/9

8. Fill in the blank(10 + 6)20 = 10(20) + 6(___)

Variables

Nita bought some candles costing $4 each. How canyou represent their total cost? Make a table toshow the cost for different quantities of candles.Use a letter such as n to represent the number ofcandles. Because n represents a quantity whosevalue can vary, it is called a variable. The total costof the candles is represented by 4 x n or 4n.

TableNumber of Candles Total Cost ($)

1 4 x 1

2 4 x 2

3 4x 3

4 4 x 4

N (any number) 4x n

Algebraic Expressions

An algebraic expression is a mathematicalexpression containing variables, numbers, andoperation symbols. Before you write analgebraic expression, identify the operation. Thetable below shows how two or more wordphrases can refer to an operation.

Word Phrase Operation Algebraic Expression

the sum of 9 and a number n

Addition 9 + n

the difference of 12 and a number n

Subtraction 12 - n

the product of 4 and a number k

Multiplication 4k

the quotient of a number divided by five

Division a5

PracticeWrite each word phrase as an algebraic expression.1) 25 more than p________ 2) the product of s and 7_______3) 14 decreased by e________4) n divided by 18__________

Evaluate each expression for b 6.5) b x 5=_______ 6) 19 + b_________ 7) 42 / b___________

For 8–11, evaluate each expression for n 3, 5, and 7.8) n -1___ ,____ ,____ 9) n + 13____ ,_____ ,______

10) 9n____ ,_____ ,_____ 11. 105/n_____,______,______

Homework