Multiplying Integers

Multiplying Integers• Let’s model integer multiplication:

2 • -3= -6 -6 • 5 = -30

Multiplying Integers

So, a positive number times a negative number is a ________ number.

Negative

And, a negative number times a positive number is a ________ number.

Negative

What is the answer to a negative times a negative?

Multiplying Integers

• Look at the pattern:-2 • 3 = -6-2 • 2 = -4-2 • 1 = -2-2 • 0 = 0-2 • -1 = ??

What is happening to the product each time?It is increasing by 2

-2 • -1 = 0 + 2 which is 2

Multiplying Integers

A negative number times a negative number is a ________ number

Positive

Multiplying Integers

Here is a way to remember it:

Good guys are +, Bad guys are –

Coming into town is +, Leaving Town is –

Good is +, Bad is -If a good guy (+) comes into town (+), that’s good (+)

If a good guy (+) leaves town (-), that’s bad (-)

If a bad guy (-) comes into town (+), that’s bad (-)

If a bad guy (-) leaves town (-), that’s good (+)

Multiplying Integers

• Multiply:4(-3)-12

-2 • -918

(-25)(6)-150

-7 • -32224

12(10)120

-16(-5)80

The Integer Song

Verse 4Here is a rule that you must know

when multiplying integers,If signs are the sameIf signs are the sameIf signs are the same

The answer’s always positive.

The Integer Song

Verse 5Another rule that you must know when

multiplying integers,If signs are differentIf signs are differentIf signs are different

The answer’s always negative.