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Introduction to negative numbers
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Introduction to negative numbers
What temperature will the thermometer show if the temperature rises 2 degrees?
What is the smallest number you can think of? Numbers that are less than zero are called negative numbers. On a thermometer, positive numbers represent temperatures above zero, and negative numbers represent temperatures below. When it's warmer than zero degrees, we use positive numbers. It is 15 degrees Celsius in the water.
Here we don't need to put a plus sign before the number. When the temperature is lower than zero, it is a negative number. It is -15 degrees Celsius in the mountains. Here, we spell out the minus sign before the number. A small raised circle is the sign for degrees, and the capital C is for Celsius.
If we turn the thermometer on it's side, the scale looks like the number line. Positive numbers are written on the right side of the number zero. Negative numbers are written on the left side of zero. The temperature in Nordben was -12 degrees on Sunday. On Monday, the temperature rose by five degrees.
What was the temperature on Monday? We look at the number line beginning at-12 and move five steps to the right, towards the positive numbers. Since it got five degrees warmer, we end up at -7. The temperature was -7 degrees on Monday. Meters above sea level is a measurement of elevation relative to sea level.
You can think of heights above sea level as positive numbers, and depths below sea level being negative numbers. The Mariana Trench in the Pacific Ocean is the world's deepest ocean trench. The trench's maximum depth is 11,024 meters below sea level. Mount Everest is the world's highest mountain. It is in the Himalayas and is 8,848 meters above sea level.
What's the difference in the elevation between The Mariana Trench and Mount Everest? We add the numbers. 11,024 plus 8,848 equals 19,872 meters. The difference in elevation is 8,872 meters. A sperm whale is swimming at a depth of 300 meters where it suddenly dives another 800 meters deeper to catch a squid.
How deep is it now? We start at -300 meters, and go down another 500 meters on the number line. And we end up at -800 meters. The sperm whale is now swimming at a 800 meter depth, or using negative numbers, at -800 meters. Think about money.
Money that you have is an asset, and positive numbers. But money that you owe is a debt, and negative numbers. You have 50 kroner and want to go to the movies. The ticket costs 100, so you borrow 50 from a friend and buy a ticket. How much money do you have now?
Let's look at the number line starting at 50. You had 50 kroner. Going 100 steps to the left. You paid 100 kroner. We end up at -50.
You are in debt, because you owe 50 kroner. We can say that you have -50 kroner. We have looked at negative numbers as temperatures below zero on the thermometer, depths below sea level, and debts. Now you know how numbers can be less that zero.