Math Lessons: Adding and Subtracting Negative Numbers

How Can I Help My Child with Adding and Subtracting Negative Numbers?

Working with negative numbers can be challenging for students because it requires a different thought process than with positive numbers. For example, students who easily recognize that eight is bigger than five may struggle to understand why negative eight is smaller than negative five. If this is the case with your child, using a number line may help him or her to complete problems more easily.

Have your child make his or her own number line by drawing a straight line across a sheet of paper. He or she should use ticks to signify intervals, and label the center tick 'zero'; all other ticks should be numbered by units of one (for example, -2, -1, 0, 1, 2). When your child has to solve an addition or subtraction problem with negative numbers, he or she can count ticks on the number line. After repeated practice, he or she may be able to do these problems in his or her head.

Sample Problems

-1 + 1 = 0

Walk your child through this problem step by step, talking aloud to model your thought process. Begin by having him or her look at a number line. Tell your child to find -1 and place a finger on it.

Then, tell him or her that the addition sign means he or she needs to slide one unit to the right. Once your child has done that, ask what number his or her finger is on now. The answer is zero; one and negative one cancel each other out.

-5 - 5 = -10

For this next problem, have your child participate as you walk through the problem. Begin by having him or her place a finger on the number line at -5. Point out that this, unlike the last problem, is a subtraction problem. Ask your child to predict which way he or she will move on the number line this time. Remember that repetition can help your child internalize the material, so reinforce the concept by restating many times that, with subtraction, he or she should move left on the number line.

-10 + 7 = -3

Now, have your child complete this problem on his or her own. He or she should begin by placing his or her finger on the number line at -10. Then, your child should add seven. Make sure he or she has slid his or her finger seven units to the right to -3.