How to Add or Subtract Negative and Positive Numbers

The concept of negative numbers can be a difficult one for some students to grasp. Demonstrating positive and negative numbers with the use of a number line is helpful in teaching the concept, and practice is helpful for reinforcing it. Follow these steps to add or subtract positive and negative numbers.

Instructions

1. Add two positive numbers together and you'll get a positive number. This is simple--three plus two equals five. If a number doesn't have a sign in front of it, assume it is a positive number.

2. Subtract positive numbers from each other. For example, four minus two equals two.

3. Understand that two negative signs or two positive signs become a positive. Therefore, you will add when asked to subtract a negative number. For example, three minus negative one equals four.

4. Remember to subtract when adding a negative number to a positive one. For example, three plus negative one is the same as three minus one, or two. The signs are different--one is positive and one is negative--so you subtract.

Tips & Warnings

• Keep practicing adding and subtracting positive and negative numbers--eventually it will become second nature.

• If you are teaching students the concept of positive and negative numbers, it's helpful to use a big graphic number line so they can "see" the concept of negative numbers and understand why adding two numbers may result in a negative number.