Lesson 2 Student Outcomes
Students model integer addition on the number line by using horizontal arrows; e.g., an arrow for is a horizontal arrow of length pointing in the negative direction.
Students recognize that the length of an arrow on the number line is the absolute value of the integer.
Students add arrows (realizing that adding arrows is the same as combining numbers in the Integer Game). Given several arrows, students indicate the number that the arrows represent (the sum).
Lesson 2 Summary
On a number line, arrows are used to represent integers; they show length and direction.
The length of an arrow on the number line is the absolute value of the integer.
Adding several arrows is the same as combing integers in the Integer Game.
The sum of several arrows is the final position of the last arrow.Exercise 1: Real-World Introduction to Integer Addition
Answer the questions below.
a. Suppose you received $10 from your grandmother for your birthday. You spent $4 on snacks. Using addition, how would you write an equation to represent this situation?
b. How would you model your equation on a number line to show your answer?
Example 1: Modeling Addition on the Number Line
Complete the steps to find the sum of -2 + 3 by filling in the blanks. Model the equation using straight arrows called vectors on the number line below.a. Place the tail of the arrow on ___.
Example 2: Expressing Absolute Value as the Length of an Arrow on the Real Number Line
a. How does absolute value determine the arrow length for -2
b. How does the absolute value determine the arrow length for 3?
c. How does absolute value help you to represent -10 on a number line?
Create a number line model to represent each of the expressions below.
a. -6 + 4
b. 3 + (-8)
Example 3: Finding Sums on a Real Number Line Model
Find the sum of the integers represented in the diagram below. Write an equation to express the suma. What three cards are represented in this model? How did you know?
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