Confidential 1 Multiplying Integers

Confidential 2 WARM-UP: 1.)5 - 9 = -4 2.)16 - (-20) = 36 3.)(-22) - 40 = )(-65) - (-81) = 16

Confidential 3 Let's review what we learned in the last lesson.

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6 We are very familiar with Addition and it is easy for us to add = 12 We can also think of this as three groups of 4 OR 3 x 4 = 12 Let's Get Started!

Confidential On a number line, this might look like x 4 = 12

Confidential 8 So, let's look at (-4) + (-4) + (-4) = -12 We know from our Addition Rules that when we add NEGATIVE numbers together, our sum is NEGATIVE. We can also look at this as three groups of (-4) OR 3 x (-4) = -12

Confidential 9 On a number line, this might look like x (-4) = (-12)

Confidential 10 But what happens when we multiply a NEGATIVE number by a NEGATIVE number?????? Multiplying by a NEGATIVE number is the opposite of multiplying by a POSITIVE number so our products have opposite signs. If 3 x (-4) = -12 Then (-3) x (-4) = +12 Remember that a "product" is the answer to a multiplication problem.

Confidential 11 Rules for Multiplying Integers The product of two integers with the SAME sign is always POSITIVE. The product of two integers with DIFFERENT signs is always NEGATIVE. 6 x 7 = +42 (-5) x (-4) = x (-4) = -32 (-9) x 3 = -27

Confidential 12 Let's try a few! Remember: SAME SIGNS Positive DIFFERENT SIGNS Negative 1.)-6 x 4 = )10 x -5 = )(-8) x (-9) = 72 4.)7 x 6 = 42 5.)-11 x 8 = -88

Confidential 13 When we multiply 3 or more numbers together, (-4) x 5 x (-2) =...we begin by multiplying 2 at a time and inserting the appropriate sign. (-20)x (-2) +40 (-4) x 5 x (-2) = +40

Confidential 14 You try some. 6 x (-10) x (-2) = 120 (-5) x 7 x 2 = -70

Confidential 15 Good! Now let's work with multi-digit numbers. -47 x 583 = larger number of digits goes on top 4 7 x x , - Let's review. Multiply first and then add the appropriate sign. Also, remember your comma! multiply from right to left

Confidential 16 You try this one! (-62) x (-941) = larger number of digits goes on top Be sure to add your COMMA and the appropriate sign X X ,3 4 2

Confidential 17 BREAK

Copyright © Ed2Net Learning, Inc. 18 GAME TIME ! Click here to play a game

Confidential 19 1.)Nancy lives 32 miles from her work. How many miles does she drive to and from work in a month? (Assume that a month has 4 weeks and Nancy works Monday through Friday.) Total miles in a day 2 X 32 = 64 (to and fro) Total number of days in a month 5 X 4 = 20 so total miles in 20 days = 64 X 20 = 1280 miles

Confidential 20 2.) Erica baked chocolate chip cookies and brought them to her girl scout meeting. The girls ate half the cookies and the troop leaders ate 5 cookies. Erica took 15 cookies home with her after the meeting. How many cookies did she take to the meeting? Erica baked 40 cookies The girls ate 20 cookies (Half of what she got.) Troop leader ate 5 so she is left with – 5 = 15

Confidential 21 3.)Susie has $232 in her bank account. She makes 3 withdrawals of $85 each. How much money must she deposit back into the account in order to have a balance of $25? Total money $232 Withdrew $85 X 3 = 255. Balance = 232 – 255 = (-23) To get balance of $25 she needs to deposit 25 – (-23) = $48

Confidential 22 Let's see how well you understood the lesson today! 1.)(-8) x 12 = )(-6) x (-20) = )2 x (-5) x 4 = )(-7) x (-3) x (-1) = )3 x (-3) x 2 x (-2) = 36 6.)32 x (-4) = -128

Confidential 23 7.) 2,903 x (-31) = 2 2, X X ,

Confidential 24 Let's review what we learned today!

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Confidential 26 Multiplying multi-digit numbers: 583 x (-47) =

Confidential 27 Great Job Today! Remember to practice what you learned!