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?

## Additional Resources

- Khan Academy: Intro to negative numbers (09:35 mins, Transcript)

### Practice Problems

**Look at the number line. Some of the numbers have been replaced with a letter. Match the letter with the correct number.**

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