Add and subtract integers using the number line
This is an introduction to integer addition and subtraction, where we use number line jumps as a model for additions and subtractions.
A jump to the right signifies addition, and a jump to the left signifies subtraction. The first number in the addition or subtraction is the starting point.
For example, 4 − 5 means that you start at 4, and jump 5 steps to the left. And -2 + 9 means that you start at -2, and jump 9 steps to the right.
This lesson does not cover the situation where you add or subtract a negative integer, such as 2 + (-4) or -3 − (-5). While those can be modeled on a number line, I personally tend to either use the shortcuts for +- and − − or to think of counters. For example, 2 + (-4) simplifies to 2 − 4 which then can be thought of as a number line jump. Similarly, -3 − (-5) simplifies to -3 + 5.
In the 2nd video, we go through some easy practice problems for integer addition and subtraction, where I instruct you to think of number line jumps to solve them.
See also
Addition of integers — a video lesson
Math Mammoth Integers — a self-teaching worktext with explanations & exercises for all operations with integers