7.8 Adding Positive and Negative Numbers Miss Hepner
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
7.8 Adding Positive and Negative Numbers
Miss Hepner
Math Message
Mental Math Reflexes
Use <, >, or = to compare numbers
1.-5 and -7
2.2.5 and -1
3.- 8/4 and -2
Adding Positive and Negative Numbers
• Objective: To develop rules for adding positive and negative numbers
• Lesson Essential Question: How do I add positive and negative numbers and what strategy can I use?
3 Strategies
• Today we will learn 3 different strategies to add positive and negative numbers. You choose the strategy that works best for you!
The three strategies include:
1. Pair and cancel (using + and – tokens)
2. Number line method
3. Subtract and Highest Sign (team and battle)
How do I add positive and negative numbers? Strategy #1
-9 + 5Pair and Cancel Method: Take nine negative tokens and five positive tokens
How do I add positive and negative numbers? Strategy #1
-9 + 5Pair a negative token with a positive token
How do I add positive and negative numbers?
-9 + 5The paired tokens cancel each other out!
Count the left over tokens and there is your answer.
How do I add positive and negative numbers?
-9 + 5 = -4
Let’s try another example using Strategy #1
-3 + 6Pair and Cancel Method: Take nine negative tokens and five positive tokens
-3 + 6Pair a negative token with a positive token
Count your left over tokens and that is your answer.
How do I add positive and negative numbers?
-3 + 6 = 3
Another way to look at it:
-9 + 5
-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1
Number Line Method
Another way to look at it:
-9 + 5 = -4
-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1
Strategy #2- Number Line
-5 + -3
-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1
Number Line Method
Strategy #2- Number Line
-5 + -3 = -8
-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1
Another way to think about it…
• Subtract the two number and take the sign of the larger:
-9 + 5 =9 – 5 = 4 (take the sign of the larger)
Answer = -4
Subtract and Highest Sign Method
Pair and Cancel Method
-3 + 7Take three negative tokens and seven positive tokens
How do I add positive and negative numbers?
-3 + 7Pair a negative token with a positive token
How do I add positive and negative numbers?
-3 + 7The paired tokens cancel each other out!
Count the left over tokens and there is your answer.
How do I add positive and negative numbers?
-3 + 7 = 4
Number Line Method
-3 + 7
-3 -2 -1 0 1 2 3 4 5 6 7
Another way to look at it:
-3 + 7 = 4
-3 -2 -1 0 1 2 3 4 5 6 7
Subtract and Highest Sign Method
• Subtract the two number and take the sign of the larger:
-3 + 7 =-3 + 7 = 4 (take the sign of the larger)
Answer = 4
Practice:
• 7 – 10
• -4 + 12
• 9 – 15
• -3 + 8
• -6x + 2x
Related Documents
