Rules for Multiplying and Dividing Negatives

Multiplying &Dividing Negatives

• Step 1: If the numbers have the same sign, the answer is positive
• 9*3 = 27
• (-9)*(-3) = 27
• 12/3 = 4
• (-12)/(-3) = 4
• Step 2: If the numbers have different signs, the answer is negative.
• 6*(-4) = -24
• (-5)*3 = -15
• 20/(-4) = -5
• (-30)/5 = -6

Tools for Adding and Subtracting Negative Numbers (+/- chart)

+/- Chart

Tools for Adding and Subtracting Negative Numbers (Number Line)

Number Line

see this explanatory video from the Khan Academy

Rules for Adding and Subtracting Negatives

Adding &Subtracting Negatives

• Step 1: simplify your signs so you only have one in between the numbers
• 9+(-2)=    >>   9-2=  
• -7+(-4)=   >>   -7-4=
• 6-(-1)=     >>   6+1=
• -5-(-3)=    >>   -5+3=
• 
  
• Step 2: circle each number and its sign
• 9-2=
• -7-4=
• 6+1=
• -5+3=
• Step 3: simplify the numbers
• If both highlighted parts are positive, add the numbers and the sign is positive.
• 6+1= 7

• If both highlighted parts are negative, add the numbers and the sign is negative.
• -7-4= -11
• If one highlighted part is positive and one is negative, subtract the small number from the large number and the sign is the same as the larger number.
• 9-2= 7
• -5+3= -2

Big Flag

How could you use math here?

(write as much as you can for 1 min. finishing this sentence)

I could use math to...

Negative Numbers

1. Make Observations & Ask Questions
1. Think: What do you notice about this graph? What questions do you have? (1 min)
2. Pair: Share your observations and questions with a partner. (1 min)
3. Share: Be ready to share 1-2 of your pair's observations with the class (2 min).
2. Define a Problem or Form a Hypothesis
1. Think: What do you think we have to know in order to be able to create and understand graphs like this? (1 min)
2. Pair: Share your hypothesis with a partner (1 min).
3. Share: Be ready to share your hypotheses with the class ( 2 min).
3. Develop a Plan
1. One of the topics we'll need to be able to understand and use in order to graph is negative numbers.
2. Draw a positive/negative sheet. I'll give you a pile of counters; make sure you have around 15-18 per person.
4. Conduct & Analyze an Experiment
1. I'll demonstrate how to use the counters and have you practice some problems about debt and the weather.
2. We'll then write number lines and discuss how to use them for adding and subtracting negative numbers.
3. We'll review how to do multiplication and division with negative numbers.
5. Communicate Results & Improve
1. Take the negative computation formative assessment to help us know how to help you improve.

Introduction

Get to Know You

Please pull out a piece of paper and answer the following questions:

1) What's your name?

2) What is your ideal career or job?

3) What are some of your hobbies or interests?

4) What are your top 3 favorite classes in school?

Turn to a partner and share one of the items you wrote down.

Two Truths and a Lie

Great, now I'd like you to make 3 bullet points and write 3 sentences about yourself. 2 of these sentences should be TRUE about yourself and 1 should be FALSE.

•  
•  
• 
  

Turn to a partner and see if they can guess which sentence is false about you, but don't mark the answer!

Please turn in your papers, and I'll see if I can guess the lie!

Beach Ball Introductions
Stand up and get in a circle and get ready to catch the beach ball and choose a question to answer!