Multiplying & Dividing Integers

Hello Sunshines!!! Get Started on Your Walk-ins! Week 4 Thursday There is a Typo on Number 4! Skip it! Get out your Notebook For Some Notes today! No Calculators Today! Don’t worry… this is the last lesson without one! 

WARMUP!! You’ve got 2.5 minutes! Remember numbers next to parenthesis means to multiply. And fractions are division questions 1. 5(8) 40 2. 6(12) 72 36 9 49 7 3. 4 4. 7 192 16 12 5. 18(7) 126 6.

You can think of multiplication as repeated addition – in fact that’s what multiplication is: a shorter way of adding the same number many times. We use this to teach young kids multiplication. For example, if three kids have 2 cookies each that would be 2 + 2 + 2 or 3∙2 so we know 3 · 2 = 2 + 2 + 2 = 6 and the same thing works with multiplying a positive times a negative: 3 · (–2) = (–2) + (–2) + (–2) = –6 Another way to think about this is if I owe three people 2 (-2) each, I owe 6 (-6) altogether!

A positive number multiplied by an integer can be written as repeated addition. 3(–200) = (–200) + (–200) + (–200) = –600 From what you know about adding and subtracting integers, you can see that a positive integer times a negative integer is negative.

Find each product. Write this example down with me! –7 · 2 Think: –7 · 2 = 2 · –7, or 2 groups of –7. –7 · 2 = (–7) + (–7) = –14 Try this one on your own! –8 · 3 –8 · 3 = (–8) + (–8) + (–8) = –24 Think: –8 · 3 = 3 · –8, or 3 groups of –8.

Find each product. –3 · 2 –5 · 3

Copy this table down!!!

MULTIPLYING AND DIVIDING INTEGERS Write this down too!!  MULTIPLYING AND DIVIDING INTEGERS If the signs are: Your answer will be: the same positive different negative SAME SIGNS = POSITIVE DIFFERENT SIGNS = NEGATIVE

Use the rule to find the answer quickly! Multiply or divide. –6(4) Signs are different. = –24 Answer is negative. –8(–5) Signs are the same. = 40 Answer is positive.

Multiply or divide. –18 2 = –9 –25 –5 = 5

Multiply or divide. 5(–2) = –10 –3(–2) = 6

Multiply or divide. –24 3 = –8 –12 –2 = 6

Copy These Questions Down for your Homework!

(-2)4

Order of Operations 1. Parentheses 2. Exponents 3. Multiply and divide from left to right. 4. Add and subtract from left to right. Remember!

Simplify. 3(–6 – 12) Subtract inside the parentheses. = 3(–18) = –54 –5(–5 + 2) = –5(–3) = 15

Simplify. –2(14 – 5) = –2(9) = –18

Simplify. 2(1 – 8) = 2(–7) = –14 4(–3 – 8) = 4(–11) = –44

Simplify. –3(6 – 9) = –3(–3) = 9

25 – (-2) ∙ -42

20 – (-3) ∙ -32

-2 ∙ 4 – 8

8 + 6 ÷ -2

Day Mon Tue Wed Thu Fri Price Change ($) –$1 $3 $2 –$5 $6 Mrs. Johnson kept track of a stock she was considering buying. She recorded the price change each day. What was the average change per day? Day Mon Tue Wed Thu Fri Price Change ($) –$1 $3 $2 –$5 $6 (–1) + 3 + 2 + (–5) + 6 = 5 5 = 1 The average change per day was $1.

Day Mon Tue Wed Thu Fri Unit Change –8 2 4 –9 6 Mr. Reid kept track of his blood sugar daily. He recorded the change each day. What was the average change per day? Day Mon Tue Wed Thu Fri Unit Change –8 2 4 –9 6 (–8) + 2 + 4 + (–9) + 6 = –5 –5 5 = –1 The average change per day was –1 unit.

Lesson Quiz – Part 1 Find each product or quotient. 1. –8 · 12 2. –3 · 5 · (–2) 3. –75 ÷ 5 4. –110 ÷ (–2) 5. The temperature at Bar Harbor, Maine, was –3° F. It then dropped during the night to be 4 times as cold. What was the temperature then? –96 30 –15 55 –12˚F

Lesson Quiz: Part 2 6. –8(4) –32 7. –12(5) –10 6 Evaluate the expressions for the given value of the variable. 8. –4t – 9 for t = –6 15 –36 t 9. for t = 9 –4 10. The temperature in Maine was –2° F. It then dropped during the night to be 10 times as cold. What was the temperature then? –20˚F