(Numbers and Operations > Operations with Rationals > Addition and Subtraction > Integers)
In the document Adding Negative Integers Using a Number Line, students use their familiarity with a number line to observe that adding two negative integers always results in a negative sum and this sum is located further to the left on the number line than the addends.
Page 1 allows students to explore various integer sums as they move an arrow along a number line. As soon as the arrow is repositioned, the student is immediately shown the related number sentence and sum.
This page can provide great classroom discourse to emphasize how each number in the addition sentence is represented by the number line and arrows. In this case, -7 is the starting number, the blue arrow is positioned at the final sum, and the number of units between the arrows is the negative integer that was added to -7.
Through the remainder of the lesson, students use a dynamic number line tool to find the sum of two or three negative integers and finally attempt a sum without the number line tool.
Students may begin to notice that the arrow is always moving to the left and therefore ask what happens when it moves to the right, which leads nicely to our integer lessons on adding a positive and a negative integer!