Multiplying Multiplying INTEGERSINTEGERS

Discovery ActivityDiscovery Activity

With a partner, complete both parts to the With a partner, complete both parts to the “Discover the Math” activity on pages 361-“Discover the Math” activity on pages 361-362362

Discovery ActivityDiscovery ActivityPart 1Part 1

What is the pattern you see?What is the pattern you see?

What is your rule for multiplying a positive number by a What is your rule for multiplying a positive number by a negative number?negative number?

Would the rule be the same for multiplying a negative Would the rule be the same for multiplying a negative number by a positive number?number by a positive number?

Part 2Part 2

What is the pattern you see?What is the pattern you see?

What is your rule for multiplying a negative number by a What is your rule for multiplying a negative number by a negative number?negative number?

Find Integer ProductsFind Integer ProductsExamplesExamplesa)a) -4 x 3 = -4 x 3 =

How: The signs are different, so the product is negativeHow: The signs are different, so the product is negative

b)b) 5 x (-2) =5 x (-2) =

How: The signs are different, so the product is negativeHow: The signs are different, so the product is negative

c)c) -7 x (-4) = -7 x (-4) =

How: The signs are the same, How: The signs are the same,

so the product is positiveso the product is positive

Vid to EnjoyVid to EnjoyMultiplying Integers Song (So Epic!)

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Applying Integer Multiplication (Problems)Applying Integer Multiplication (Problems)

ExampleExample

• Six students each owe $5 forSix students each owe $5 for

a field trip. What is the totala field trip. What is the total

amount owed? What integeramount owed? What integer

rule does this illustrate?rule does this illustrate?

• Solution:Solution:• 6 x (-5) = -306 x (-5) = -30• The six students owe a total of $30. This is -$30. The six students owe a total of $30. This is -$30.

This illustrates that the product of a positive number This illustrates that the product of a positive number and a negative number is negative.and a negative number is negative.

Multiplying More Than 2 IntegersMultiplying More Than 2 IntegersExamplesExamples

a)a) 5 x (-9) x (-3)5 x (-9) x (-3)

= -45 x (-3)= -45 x (-3)

= 135= 135

b)b) -2 x (-4) x (-7) x 2-2 x (-4) x (-7) x 2

= 8 x (-7) x 2= 8 x (-7) x 2

= -56 x 2= -56 x 2

= -112= -112

• I used the order of operations and multiply from left to I used the order of operations and multiply from left to right.right.

Multiplication RulesMultiplication Rules• When you multiply 2 integers,When you multiply 2 integers,

If the signs are the same, the product is positiveIf the signs are the same, the product is positive

(5 x 5 = 25; -4 x (-4) = 16)(5 x 5 = 25; -4 x (-4) = 16)

If the signs are different, the product is negativeIf the signs are different, the product is negative

(5 x (-5) = -25; -5 x 5 = -25)(5 x (-5) = -25; -5 x 5 = -25)