Teaching Ideas for How to Add and Subtract Integers

Addition and subtraction are at the foundation of any student's understanding of math, but throwing negative integers into the mix can cause a lot of confusion until you understand the rules. A lot of creative ways exist to teach adding and subtracting integers to children. Teachers should aim for students to understand the concept of working with negative integers, not just memorizing the rules. This can be achieved though illustration of what is going on and real-life examples.

  1. Counters

    • Students can visualize what each number in an equation represents using counters. Create counters using bingo chips, cardboard or whatever material you have that can be cut out into small circles. Mark half of the counters with a "+" and half with a "-". Give students an equation, for example 3 - 4. Have the class lay out three "+" counters to represent the first number in the equation. Next, have them place four "-" counters underneath the row of positive counters. Tell the class that each "+" and "-" that are lined up with each other are canceled out and that the answer will be whatever is left. For this example, the class will have one "-" chip left, so the answer is -1.

    Number Line

    • A number line is a useful tool for teaching the addition and subtraction of integers. Draw a number line on the whiteboard and provide each student with his own number line. Give the students a problem to solve, for example -2 + 3. Have everyone in the class point to the first number in the equation, in this case -2. Next, have the class add 3 by moving three spots to the right on the number line. Whatever number the student is now pointing to should be the correct answer. You can practice moving around a number line by asking students to "add 3," then "subtract 4," and so on.

    Real-Life Examples

    • It is always important to apply math lessons to real life situations. It can be tricky to find good example problems that involve negative numbers. Temperature is a good example of a negative set of numbers that we use in our daily lives. Have students add 3 degrees to -20 degrees. Ask students to subtract 10 degrees from 3 degrees. Treat the thermometer as a number line when you help students answer these equations.

    Bad Behavior and Double Negatives

    • The most confusing rule to explain when adding and subtracting integers is that a double negative equals a positive. Having the students memorize the rules may help them remember it for a quiz, but using an example will help the class conceptualize what the rule is really talking about.

      Use the example of a bad student trying to become a better person. Say, in this example, that a student is loud and rude, two negative qualities (-2). This student, however, wants to become a better person so he chooses to no longer be loud. He is subtracting a negative quality about himself (- -1). The student is now only rude, one negative quality. Therefore, the answer to -2 - -1 is -1.

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