Addition and Subtraction:

Introduction to Positive and Negative Numbers

Why do we have negative numbers?

In history, people have not always had negative numbers. Ancient Greek mathematicians didn’t believe in negative numbers. In AD 620, Indian mathematicians developed the first rules for negative numbers.

Negative numbers are very useful. They are used in finances to express debt. They can also be used to express a payment.

Negative numbers are also used in temperatures. In Celsius, zero represents the freezing point for water. As it gets warmer, the numbers increase in the positive direction. When the temperature is below freezing, the numbers are negative.

Critical Thinking Question

What is another example of a negative number? When have you used a negative number in your own life?

Video Source (01:52 mins) | Transcript

Additional Resources

Practice Problems

  1. Look at the number line. Some of the numbers have been replaced with a letter. Match the letter with the correct number.
This picture is of a long horizontal line with short vertical lines spaced evenly representing the whole numbers on a number line. We will call these vertical lines hash marks. The center most hash mark has a 0 below it. The other hash marks going to the left and right of this center mark also have either numbers or letters below them. The first hash mark to the right of 0 has a 1. The second hash mark to the right has a B. The third hash mark has a 3. These are followed by D, E, and 6 going to the right. The hash mark to the left of 0 has A under it. The second hash mark to the left has negative 2 under it. This pattern continues with C, negative 4, F, and negative 6 going further and further to the left.

Solutions

  1. A = \(-1\), B = 2, C = \(-3\), D = 4, E = 5, F = \(-5\) (Solution Video | Transcript)