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Negative number

math Maturity 7-9 Next article →

Imagine you have nothing in your hands. In math, we call this zero. But what if you actually owe someone something? You might owe a friend three cookies. This idea of owing is a negative number. A negative number is any value that is less than zero.

Number-line
Number-line

We usually write these numbers with a small minus sign in front. For example, we write -3 to mean negative three. These numbers help us show the opposite of a positive number. Positive numbers are greater than zero, while negative numbers are smaller.

AdditionRules
AdditionRules

We can see these numbers working in many parts of our world. On a thermometer, negative numbers show temperatures that are colder than zero.

US Navy 070317-N-3642E-379 During the warmest part of the day, a thermometer outside of the Applied Physics Laboratory Ice Station's (APLIS) mess tent still does not break out of the sub-freezing temperatures
US Navy 070317-N-3642E-379 During the warmest part of the day, a thermometer outside of the Applied Physics Laboratory Ice Station's (APLIS) mess tent still does not break out of the sub-freezing temperatures

In a building, an elevator might use negative numbers for floors below the ground.

Elevator Negative Floor Numbers in Ireland (16785350923)
Elevator Negative Floor Numbers in Ireland (16785350923)

Sports fans use them too. In racing, a negative time can mean a driver was faster than before.

Spanish Grand Prix, 2014
Spanish Grand Prix, 2014

Even in money, a negative balance means you have a debt. This is sometimes called being "in the red."

Math has special rules to make sure these numbers work correctly. When you add two negative numbers, it is like combining two debts. If you owe two dollars and then owe three more, you owe five total.

AdditionRules
AdditionRules

You can also multiply them using specific rules. If you multiply one positive and one negative number, the answer is negative. However, if you multiply two negative numbers, the answer becomes positive. This happens because a negative sign can act like a change in direction.

Multiplication of Positive and Negative Numbers
Multiplication of Positive and Negative Numbers

These rules help keep our math logical and consistent.

People have been studying these ideas for a very long time. Very old Chinese math books from the Han dynasty used negative numbers. A person named Liu Hui lived around the 3rd century. He helped create rules for adding and subtracting them. Later, Indian mathematicians like Brahmagupta used them in the 7th century. Islamic mathematicians also worked on rules for multiplying negative numbers. Before these discoveries, some thinkers thought negative solutions were just "false" or absurd.

To visualize how they work, we use a number line. Zero sits right in the middle of the line. Positive numbers live to the right side of zero. Negative numbers live on the left side of zero.

Number-line
Number-line

As you move further left, the numbers get smaller. This means a number like -10 is actually smaller than -3. Even though ten is a big number, negative ten is very low. This helps us understand how values change on a scale. It makes the concept of "less than zero" very clear.

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🖼️ Images & Media (6)
File:US Navy 070317-N-3642E-379 During the warmest part of the day, a thermometer outside of the Applied Physics Laboratory Ice Station's (APLIS) mess tent still does not break out of the sub-freezing temperatures.jpg
US Navy 070317-N-3642E-379 During the...
File:Number-line.svg
Number-line.svg
File:Spanish Grand Prix, 2014.jpg
Spanish Grand Prix, 2014.jpg
File:Elevator Negative Floor Numbers in Ireland (16785350923).jpg
Elevator Negative Floor Numbers in...
File:AdditionRules.svg
AdditionRules.svg
File:Multiplication of Positive and Negative Numbers.svg
Multiplication of Positive and Negative...
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