Math Journal 8-13-14

Find the perimeter of the trapezoid:4x ft

3x ft

3x ft

60x in

UNIT 1 DAY 3: EVALUATING EXPRESSIONS WITH MULTIPLYING AND DIVIDING INTEGERS

Essential Questions: What are the rules for multiplying and dividing integers? How do you

substitute a number for a variable?

Product: the answer obtained by multiplying two or more quantities.

Factor: the numbers and variables that are multiplied in an expression.

Quotient: the answer obtained by dividing two or more quantities.

Vocabulary

Multiplying and Dividing Integers

To figure out the signs when multiplying or dividing integers, use the following rules:

Same Signs: Positive

Different Signs: Negative

If you have more than two negative factors…

Even # of negatives = positive

Odd # of negatives = negative

Example 1

a) -8(2) b) -5(-7)

c) 12(9) d) (1/2)(-18)

-16 35

108 -9

Example 2a) b)

c) d)

6 -10

-9 7

Evaluating Expressions

To evaluate an expression:

1) Substitute each variable with the given number.

2) Simplify the expression to a single value.

Example 3Evaluate the following expressions when a = 12, b = -3, and c = 24.

a) 6/b b) a/b

c) c/-b d) b(c/a)

6/-3

-2

12/-3

-4

24/38

-3(24/12)

-3(2)

-6

Example 4

The plane’s height above the ground (in thousands of feet) equals the distance from the

airport (in miles) that a plane should begin descending divided by 3.

height = distance/3

If a plane is 30 miles from the airport when the pilot begins to land the plane, what is the plane’s height above ground in thousands of feet?

h

The plane is 10 thousand feet above

the ground.

height = 30/3

Summary

Essential Questions: What are the rules for multiplying and dividing integers? How do you substitute a number for a variable?

Use 1 minute to write 2 sentences answering the essential questions.