Article Summary: "The idea of negative numbers has been around for a long
time. The ancient Chinese people used negative numbers in the marketplace.
In fact they used red counting rods for positive numbers and black counting
rods for negative numbers. It wasn't until centuries later, in the 16th
century, that mathematicians outside of China started using negative numbers."
When you were about two years old you probably learned to hold up two fingers when you were asked how old you were. Two fingers are real and in this case represented two years of time. From the very beginning of civilization numbers were meant to count real things, like the number of sheep when sheep were being sold or traded. Then zero meant none, no sheep. In today's mathematics numbers that are greater than zero are called positive numbers.
Let's think about subtraction for a minute where we "take away" a number. Pretend you want to buy some music CD's from your friend who has 8 CD's for sale. While there are 8 CD's for sale you want to buy just 6 of them. You "take away" 2 CD's and the math is 8 - 2 = 6. Another way to look at your CD trading transaction is -2 or negative 2. Is the negative number real? Your friend who was selling CD's still has 2 CD's so it's okay to decide that the negative number is real.
The idea of negative numbers has been around for a long time. The ancient Chinese people used negative numbers in the marketplace. In fact they used red counting rods for positive numbers and black counting rods for negative numbers. It wasn't until centuries later, in the 16th century, that mathematicians outside of China started using negative numbers.
Are you familiar with the term sea level? The location of sea level is determined by scientists. Picture yourself standing on a high cliff looking out over the ocean and feeling the nice ocean breezes. How far is it down to the water? If it's 30 feet to the water you are 30 feet above sea level. But the exact science of sea level is a bit more complicated than this simple example.
The tallest mountain in the world, Mount Everest, is 29,035 feet above sea level. Flat areas in the middle of the United States sometimes are only 600 feet above sea level! The lowest point in the United States is Death Valley which is located in both California and Nevada. Death Valley is 282 feet below sea level or -282 feet in relation to sea level.
Based on the examples of selling CD's and sea level, you know that negative integers make sense. But does it make sense to have a negative decimal number like -17.56? It certainly does!
Negative numbers are used a lot in banking and finance. It's easy to think of positive numbers as plus or addition and negative numbers as minus or subtraction. Do your parents use an ATM machine? Money doesn't flow from an ATM machine by magic, does it? Your parents deposit money in the bank and when they withdraw money from the bank at the ATM machine, the amount is subtracted from their account. Basically any withdrawal from a bank account is a negative number. Since dollars and cents are shown as decimal numbers, it's easy to see that negative decimal numbers make sense.
In fact, all electronic banking transactions are based upon the idea of positive and negative numbers. Banks really don't transfer actual dollar bills very often. Banks send computer messages to each other that credit an account with a positive number or debit an account with a negative number. But when banks or other financial companies prepare printed statements, they use the opposite color scheme from the ancient Chinese. Today black is used for positive numbers and red is used for negative numbers.
So, negative numbers are extremely important in you and your family's everyday life. Now you know that negative numbers exist for sure.